Parliamentary privilege (also absolute privilege) is a legal immunity enjoyed by members of certain legislatures, in which legislators are granted protection against civil or criminal liability for actions done or statements made in the course of their legislative duties. It is common in countries whose constitutions are based on the Westminster system. A similar mechanism is known as parliamentary immunity.
In the United Kingdom, it allows members of the House of Lords and House of Commons to speak freely during ordinary parliamentary proceedings without fear of legal action on the grounds of slander, contempt of court or breaching the Official Secrets Act. It also means that members of Parliament cannot be arrested on civil matters for statements made or acts undertaken as an MP within the grounds of the Palace of Westminster, on the condition that such statements or acts occur as part of a proceeding in Parliament—for example, as a question to the Prime Minister in the House of Commons. This allows Members to raise questions or debate issues which could slander an individual, interfere with an ongoing court case or threaten to reveal state secrets, such as in the Zircon affair or several cases involving the Labour MP Tam Dalyell.
There is no immunity from arrest on criminal grounds, nor does the civil privilege entirely extend to the devolved administrations in Scotland or Wales. A consequence of the privilege of free speech is that legislators in Westminster systems are forbidden by conventions of their House from uttering certain words, or implying that another member is lying. (See unparliamentary language.)
The rights and privileges of members are overseen by the powerful Committee on Standards and Privileges. If a member of the House is in breach of the rules then he/she can be suspended or even expelled from the House. Such past breaches have included giving false evidence before a committee of the House and the taking of bribes by members.
Similar rights apply in other Westminster system countries such as Canada and Australia. In the United States, the Speech or Debate Clause in Article One of the United States Constitution provides for a similar privilege, and many state constitutions provide similar clauses for their state legislatures.
Parliamentary privilege is controversial because of its potential for abuse; a member can use privilege to make damaging allegations that would ordinarily be discouraged by defamation laws, without first determining whether those allegations have a strong foundation. A member could, even more seriously, undermine national security and/or the safety of an ongoing military or covert operation or undermine relations with a foreign state by releasing sensitive military or diplomatic information.
Privileges of the UK House of Commons
The ancient and undoubted rights and privileges of the Commons are claimed by the Speaker at the beginning of each new Parliament. The privileges are only codified in Erskine May's Parliamentary Practice and the House itself is the only judge of its own privileges. Most of those specifically claimed are practically obsolete, but others remain very real:
- Freedom of speech; (members speaking in the House are not liable for defamation)
- Freedom from arrest in civil matters (practically obsolete);
- Access of the Commons to the Crown (via the Speaker); and
- That the most favourable construction should be placed upon the deliberations of the Commons.
Privileges not specifically mentioned:
- Right of the House to regulate its own composition; (although election petitions are now determined by the ordinary Courts)
- Right of the House to regulate its own internal proceedings, both as to matters and procedures;
- Right to punish members and “strangers” for breach of privilege and contempt;
- Right of freedom from interference (although members are no longer immune from all civil actions)
There is an absolute common law privilege for papers circulated among MPs by order of the House (Lake v. King (1667) 1 Saunders 131). This is extended to all papers published under the House's authority, and to correct copies by the Parliamentary Papers Act 1840. The Act also extends qualified privilege to extracts.
In addition to applying to members speech within the chamber, parliamentary privilege also applies to select committees. Written and oral evidence given to, and published by these committees is also subject to the same absolute privilege as parliamentary papers. This means that any evidence given by a witness to a select committee may not be used against them or any other person in a court of law, whether for civil or criminal proceedings. This privilege only applies, however, if the committee has formally accepted it as evidence and does not apply to materials published before they were given to the committee.
Parliamentary privilege in Canada
In Canada, the Senate and House of Commons and provincial legislative assemblies follow the definition of parliamentary privilege offered by the British parliamentary authority, Erskine May's Treatise on The Law, Privileges, Proceedings and Usage of Parliament, which defines parliamentary privilege as "the sum of the peculiar rights enjoyed by each House collectively as a constituent part of the High Court of Parliament, and by Members of each house individually, without which they could not discharge their function... the privileges of Parliament are rights which are absolutely necessary for the due execution of its powers. They are enjoyed by individual Members, because the House cannot perform its functions without unimpeded use of the service of its Members, and by each House for the protection of its members and the vindication of its own authority and dignity." Parliamentary privilege can therefore be claimed by Members individually or by the House collectively.
The rule for when parliamentary privilege applies is that it cannot exceed the powers, privileges and immunities of the imperial parliament as it stood in 1867, when the first constitution was written. 
Individual parliamentary privileges include:
- Freedom of speech
- Freedom from arrest in civil action
- Exemption from jury duty
- Exemption from appearing as a witness
- Freedom from obstruction, interference, intimidation and molestation
Collective parliamentary privileges include:
- Power to discipline
- Regulation of the House’s internal affairs
- Management of Employees
- Authority to maintain the attendance and service of Members
- Right to institute inquiries and to call witnesses and demand papers
- Right to administer oaths to witnesses
- Right to publish papers containing defamatory material
The Supreme Court of Canada has previously dealt with the question of parliamentary privilege in New Brunswick Broadcasting Co. v. Nova Scotia (Speaker of the House of Assembly). In that case, the Court made these observations about parliamentary privilege:
“Privilege” in this context denotes the legal exemption from some duty, burden, attendance or liability to which others are subject. It has long been accepted that in order to perform their functions, legislative bodies require certain privileges relating to the conduct of their business. It has also long been accepted that these privileges must be held absolutely and constitutionally if they are to be effective; the legislative branch of our government must enjoy a certain autonomy which even the Crown and the courts cannot touch.
The privileges attaching to colonial legislatures arose from common law. Modelled on the British Parliament, they were deemed to possess such powers and authority as are necessarily incidental to their proper functioning. These privileges were governed by the principle of necessity rather than by historical incident, and thus may not exactly replicate the powers and privileges found in the United Kingdom.
Recent cases of parliamentary privilege in Canada adjudicated by the courts include:
- 1993: New Brunswick Broadcasting Co. v. Nova Scotia (Speaker of the House of Assembly), where the courts held parliament could restrict who could enter the parliamentary precincts.
- 1999: Zundel v. Boudria, et al., where the courts held parliament could restrict who could enter the parliamentary precincts.
- 2001: Ontario (Speaker of the Legislative Assembly) v. Ontario (Human Rights Commission), where the courts held the actions of the provincial legislative assembly were immune from review by other government bodies including the Human Rights Commission.
- 2005: Canada (House of Commons) v. Vaid, where the Supreme Court of Canada analyzed the scope of parliamentary privilege and the role of courts in deciding its existence.
Parliamentary privilege in Australia
In 1904, the Parliament of Western Australia imprisoned John Drayton for three weeks for a breach of parliamentary privilege.
In 1955, a newspaper proprietor Raymond Fitzpatrick and his editor Frank Browne were jailed by the Australian House of Representatives for three months for what the House considered a gross breach of parliamentary privilege. The public and most commentators, then and since, felt the punishment far outweighed the crime.
- Sir Thomas Haxey – free speech 
- Richard Strode (Privilege of Parliament Act) 
- George Ferrers – debt default 
- Stockdale v. Hansard – defamation by Hansard 
- Charles Bradlaugh – Oath of Allegiance 
- Duncan Sandys – free speech 
- Archibald Maule Ramsay – treason 
- Garry Allighan – defamation 
- Duncan Campbell (the Zircon affair) – free speech 
- Neil Hamilton – Cash for Questions 
- Bill Heffernan – free speech 
- "Superinjunction" controversy":
- The Guardian–Trafigura affair - Right of the media to report proceedings covered by parliamentary privilege 
- Fred Goodwin v News Group Newspapers Ltd and VBN and CTB v News Group Newspapers (Ryan Giggs) - Right of the media to report on anonymised court injunctions; parliamentary privilege used to allow the media to report the existence of injunctions and the parties involved 
- An unnamed injunction in 2006 granted preventing participants of a case from speaking to individuals including "Members of Parliament, journalists, lawyers" on toxic chemicals in passenger ship water tanks and resulting illnesses – Right of constituents to speak to their MPs; existence revealed in a parliamentary question several years later. 
- Ryan Giggs, a footballer, was suspected of committing adultery with Imogen Thomas, a Big Brother contestant, sought an injunction to prevent the media talking about the issue. He took legal action against Twitter, given that a Twitter user had named him among several celebrities as having taken out super-injunctions. Large numbers of people retweeted the comments and eventually, the Liberal Democrat MP John Hemming used parliamentary privilege to name Ryan Giggs. No prosecutions against Twitter users were pursued, firstly because of the impracticality of pursuing things and secondly because of the public outcry about sleazy celebrities using super-injunctions to evade accountability for sleazy behaviour.
- "Speaker's Statement". House of Commons Daily Debates. Hansard. 3 December 2008. Retrieved 5 December 2008. "I should also remind the House, as stated in chapter 7 of “Erskine May,” that parliamentary privilege has never prevented the operation of the criminal law. [Interruption.] Order. The Joint Committee on Parliamentary Privilege in its authoritative report in 1999 said that the precincts of the House are not and should not be “a haven from the law”."
- "How Parliament works". www.parliament.uk. Retrieved 10 May 2011.
- British Council India's LEGAL eNEWS Theme article comparing British and Indian perspectives
- Australia's Parliamentary Privileges Act 1987
- Josh Chafetz, Democracy's Privileged Few: Legislative Privilege and Democratic Norms in the British and American Constitutions (Yale Univ. Press 2007) (ISBN 0-300-11325-0)
- Simon Wigley, 'Parliamentary Immunity: Protecting Democracy or Protecting Corruption?,' Journal of Political Philosophy, Vol. 11, No.2, pp. 23–40.
- Erskine May, Parliamentary Practice: The Law, Privileges, Proceedings and Usage of Parliament, W.R. Mackay et al. (eds) (London: Butterworths, 2004) (ISBN 0-406-97094-7)
- UK Parliament, Reports of the Joint Committee on Parliamentary Privilege in Session HL 43-I/ HC 214-I. (London: The Stationary Office Limited, 1999).
- Marc Van der Hulst, The Parliamentary Mandate. (Geneva: Inter-Parliamentary Union, 2001) (ISBN 92-9142-056-5)
- Centre for Constitutional Studies, 'Parliamentary Privilege' 
Management of employees This privilege was considered in the South Australian Industrial Relations Court in the case of Kosmas v Legislative Council (SA) and Others  SAIRC 86. The Court found that employment statutes apply to the Parliament and therefore employees can seek judicial relief for matters such as unfair dismissal or workers compensation.