A public inquiry, also known as a tribunal of inquiry, government inquiry, or simply inquiry, is an official review of events or actions ordered by a government body. In many common law countries, such as the United Kingdom, Ireland, Australia and Canada, such an inquiry differs from a royal commission in that a public inquiry accepts evidence and conducts its hearings in a more public forum and focuses on a more specific occurrence. Interested members of the public and organisations may make (written) evidential submissions, as is the case with most inquiries, and also listen to oral evidence given by other parties.
Typical events for a public inquiry are those that cause multiple deaths, such as public transport crashes or mass murders. In addition, in the UK, the Planning Inspectorate, an agency of the Department for Communities and Local Government, routinely holds public inquiries into a range of major and lesser land use developments, including highways and other transport proposals.
Advocacy groups and opposition political parties are likely to ask for public inquiries for all manner of issues. The government of the day typically only accedes to a fraction of these requests. The political decision whether to appoint a public inquiry into an event was found to be dependent on several factors. The first is the extent of media coverage of the event; those that receive more media interest are more likely to be inquired. Second, since the appointment of a public inquiry is typically made by government ministers, events that involve allegations of blame on the part of the relevant minister are less likely to be investigated by a public inquiry. Third, a public inquiry generally takes longer to report and costs more on account of its public nature. Thus, when a government refuses a public inquiry on some topic, it is usually on at least one of these grounds.
The conclusions of the inquiry are delivered in the form of a written report, given first to the government, and soon after published to the public. The report will generally make recommendations to improve the quality of government or management of public organisations in the future. Recent studies have shown that the reports of public inquiries are not effective in changing public opinion regarding the event in question. Despite claims that appointing a public inquiry leads to a decline in media attention to the inquired issue, empirical studies do not find support for this claim.  Public inquiry reports appear to enjoy public trust only when they are critical of the government, and tend to lose credibility when they find no fault on the part of the government.
In France, any major project which requires the compulsory acquisition of private property must, before being approved, be the subject of a public inquiry (usually by the prefect of the region or department in which the project will take place); the favourable outcome of such an inquiry is a déclaration d'utilité publique, a formal finding that the project will produce public benefit. This procedure was established by the law on expropriation enacted on 7 July 1833, which extended an earlier law enacted in 1810.
Republic of Ireland
In Ireland, there are several kinds of public inquiry. A Tribunal of Inquiry, often simply called a tribunal, is a powerful type of statutory inquiry whose procedures are governed by the Tribunals of Inquiry (Evidence) Act 1921 as amended. An Oireachtas inquiry is a less powerful non-statutory inquiry controlled directly by the Oireachtas (parliament). A 2013 proposal to strengthen the power of Oireachtas inquiries was defeated at a referendum. The Law Reform Commission published a report in 2005 examining the operation of public inquiries and recommending changes. A commission of investigation is a different form of inquiry, with evidence generally given in private; provided by the Commissions of Investigation Act 2004 to address scandals relating to medical care and child abuse.
A number of historically important public inquiries have taken place in South Africa since the advent of full democracy in 1994. A number of which have looked into national scale events such as systematic human rights abuses during apartheid or wide scale corruption.
In the United Kingdom, the term public inquiry refers to either statutory or non-statutory inquiries that have been established either previously by the Monarch or by government ministers of the United Kingdom, Scottish, Northern Irish and Welsh governments to investigate either specific, controversial events or policy proposals. Non-statutory public inquiries are often used in order to investigate controversial events of national concern, the advantage being that they are more flexible than the statutory inquiry as they do not need to follow the requirements of the Inquiries Act 2005, The Inquiry Rules 2006 (UK, excluding Scotland) and The Inquiries (Scotland) Rules 2007. Statutory inquiries can be held as subject-specific public inquiries, however most are now held under the Inquiries Act 2005 which repealed the Tribunals of Inquiry (Evidence) Act 1921. This list excludes Public Local Inquiries (which encompasses Planning Inquiries, Compulsory Purchase Order Inquiries, Listed Building Inquiries etc.)Only United Kingdom government ministers can establish public inquiries, set their terms of reference, and appoint the chair. The UK Government considers that the main purpose of public inquiries is in “preventing recurrence”. Between 1990 and 2017 UK governments spent at least £630m on public inquiries, with most expensive being the Bloody Sunday Inquiry costing £210.6 million. Most public inquiries take about two years to complete their work. The Hammond Inquiry into ministerial conduct relating to the Hinduja affair in 2001 has been the shortest inquiry, taking just 45 days to report its findings. The Inquiry into Hyponatraemia-related Deaths in Northern Ireland is the longest, which took 13 years and three months to conclude.
In Hong Kong, the Commissions of Inquiry Ordinance was enacted for establishing such a commission. The commission established after the 2012 Lamma Island ferry collision produced a report of its findings which they made public; an internal report was kept confidential. In the 2019–20 Hong Kong protests, one of the five key demands of the protesters, was establishing another commission for the protests itself.
- Inquest, a similar investigation with lesser scope
- Royal Commission
- Inquiries Act 2005 (UK statute which provides for the holding of inquiries)
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