There have been four such arrangements, and one alleged proposal, at the national level. In many local councils in the UK there are similar arrangements, although there are also arrangements where the Lib Dems and Labour oppose each other and instead form a local alliance with another party or with independent councillors.
19th century 
Before the Labour Party had been formed, various candidates stood for Parliament with backing of the Liberal Party and the Labour Representation League, including Thomas Burt, Harry Broadhurst and Alexander Macdonald. These MPs were referred to as 'Lib–Lab', although there was not a formal 'pact'.
20th century 
In 1903 an agreement was made between Herbert Gladstone (then Chief Whip of the Liberal Party) and Ramsay MacDonald (Secretary of the Labour Representation Committee) that, in thirty constituencies, the Labour Party and the Liberal Party would not stand against each other, and thus risk splitting their vote. As a result of this agreement, in contests against the Conservative party, 29 Labour MPs were returned at the general election of 1906.
In the 1923 general election, both parties campaigned on the issue of free trade. The Conservatives, who had campaigned to introduce protective tariffs, lost their parliamentary majority but remained the largest party. The Liberals agreed to enable the formation of the first Labour government in 1924 under Ramsay MacDonald.
In the 1929 general election, Labour won the greatest number of seats, though not a parliamentary majority. The now much weakened Liberals allowed the formation of the second Labour government by not allying with the Conservatives to defeat the new government.
In March 1977 the Labour Government, left with no overall majority following a by-election defeat, faced a motion of no confidence. In order to remain in office, Prime Minister James Callaghan approached the Liberal Party under the leadership of David Steel. Callaghan had been prime minister for just one year, having succeeded Harold Wilson who had led Labour to a three-seat majority in October 1974.
An agreement was negotiated, under the terms of which the Labour Party accepted a limited number of Liberal Party policy proposals and in exchange, the Liberal Party agreed to vote with the government in any subsequent motion of no confidence. While this 'pact' was the only official bi-party agreement since the Second World War (until the Conservative–Lib Dem coalition following the 2010 election), it fell far short of a coalition. The Lib–Lab Pact's end was confirmed on 7 September 1978, by which time Callaghan was expected to call a general election, but instead he decided to continue as leader of a minority government until May 1979, when after a vote of no confidence it was forced to hold a general election, in which Margaret Thatcher led the Conservatives back into power.
Proposed coalition of 1997 
In the lead up to the 1997 general election, a coalition government was discussed by Tony Blair and the Lib Dems, according to Paddy Ashdown's The Ashdown Diaries. Ashdown, a strong proponent of a Lib-Lab coalition, said that from Blair's point of view, in order to get the Conservatives out of power and because he wanted to move his party towards the New Labour ideal, a coalition would strengthen his majority in the likely event of a victory. To get the Liberal Democrats into his Cabinet, he allegedly agreed on their terms of electoral reform. Tony Blair was still considering attempting to form a coalition government with the Liberal Democrats on the day of the general election, until the full scale of his Labour Party's majority became clear. It is alleged that Blair still harboured thoughts of getting the Lib Dems into Cabinet, but that John Prescott's resignation threat stemmed this.
21st century 
Proposed coalition of 2010 
After the hung parliament in 2010, the Liberal Democrats, as they had indicated they would do so prior to the election, first began negotiations with the Conservatives - as the party which won the most votes and seats - about the possibility of forming a government; but, after talks appeared to have stalled, complementary negotiations were undertaken with Labour.
Labour's delegation for negotiations included Peter Mandelson, Andrew Adonis, Ed Miliband, and Ed Balls. Press rumours of a possible Lib Dem-Labour deal were publicised, with Gordon Brown alleged to be willing to offer a form of Proportional Representation if an arrangement which would have kept him in government could be agreed.
A Lib-Lab coalition would, however, have been eight seats short of a majority. A coalition of Labour, the Liberal Democrats, the SDLP, the Alliance Party of Northern Ireland and the Green Party - a "rainbow" or "traffic light" coalition - would have therefore been needed to give even the smallest possible majority. For this, amongst other reasons, the talks failed. On the collapse of talks with Labour, a deal between the Liberal Democrats and Conservatives was reached (subsequently being approved by Liberal Democrats members at a special party conference).
There was a significant level of hostility to such a deal within the Labour party with coalition proposals being opposed by, among others, former cabinet ministers John Reid, Alan Johnson, David Blunkett and former leader Neil Kinnock. John Reid said that such a coalition would be "bad for the country".
David Laws, chief negotiator for the Liberal Democrats in coalition negotiations, subsequently commented on Labour's preparation and conduct in negotiations - his main areas of criticism centred on Labour's lack of contrition about their record over the previous thirteen years, inadequate preparation for discussions, their unwillingness to accommodate Liberal Democrat policy proposals in the potential programme for government, and the arrogant and patronising attitude of specific key Labour figures. Specifically he said that whilst Gordon Brown was quite serious about pursuing talks, he accused former minister Ed Balls of "sabotaging" the talks.
Possible coalition after 2015 general election 
The party that wins the most votes but fails to get an absolute majority in the house has the right to attempt to form a government first, either on their own or in a coalition Nick Clegg stated prior to the 2010 election. He has also stated his willingness to work with the Labour party if in the next parliament they win a plurality of the votes. This is however unlikely under the leadership of Nick Clegg as both Ed Miliband and Ed Balls have spoken of unhappiness with Nick Clegg because of his partnership with David Cameron. In a Liberal Democratic member poll in the summer of 2012, 48 percent of polled members said they would be in favour of a partnership with the Labour party if the next election ends in a hung parliament.
National Assembly for Wales 
When the first elections to the new Welsh Assembly took place in 1999 no one party had an absolute majority, and initially Labour sought to run a minority administration. Following a series of close votes and much criticism of the weakness of the Assembly administration, Labour and the Liberal Democrats formed a coalition in October 2000 with the two parties sharing power, including ministerial appointments, with Labour the majority party. The agreement ended at the elections of 2003 when Labour won 50% of the seats and decided to form a minority government.
Scottish Parliament 
In 1999, after the first general election to the reconvened Scottish Parliament in July of that year, the Lib Dems signed up to what was termed a "partnership government" with Labour, with both parties providing ministers in a shared government.
Although standing on separate manifestos in the succeeding general election of 2003 the joint working continued, with Labour's Jack McConnell serving as First Minister, and the Lib Dems' Jim Wallace serving under him as Deputy First Minister (and Minister for Enterprise and Lifelong Learning) who was then succeeded by Nicol Stephen of the same party as Deputy First Minister.
The 2007 general election saw the Scottish National Party surpass Labour as the largest party by one seat. The Scottish Liberal Democrats decided against coalition with either the SNP or Labour, and abstained in the vote for First Minister, won by Alex Salmond
Constitutional committee 
Whilst not a pact, ahead of the 1997 election Labour Leader Tony Blair and Lib Dem leader Paddy Ashdown set up the Labour-Liberal Democrat joint committee on constitutional reform to discuss devolution in Wales and Scotland, and led to Prime Minister Tony Blair setting up a joint Lib–Lab cabinet committee. In part this led to the Scottish and Welsh alliances noted above. The committee was disbanded by Tony Blair and Charles Kennedy in September 2001.
- "1978: Callaghan accused of running scared". BBC News. 1978-09-07.
- Wheeler, Brian (2007-05-10). "The Tony Blair story". BBC News Online. Retrieved 2007-05-14.
- Savage, Michael (2009-11-23). "Clegg reveals Lib Dems are prepared to back Cameron". The Independent (London).
- "Labour 'ready to concede defeat'". BBC News. 2010-05-11.
- Travis, Alan (2010-05-10). "Con-Lib or Lib-Lab – how the rival coalition deals might work". The Guardian (London).
- Wintour, Patrick (2010-05-11). "Coalition talks: Labour revolt may scupper deal with Liberal Democrats". The Guardian (London).
- "John Reid: Lib-Lab coalition 'bad for the country'". ITN News @ YouTube. May 10, 2010.
- Bradley, Ruth (2010-11-23). "Balls "sabotaged" coalition talks". BBC News.
- "Clegg does not rule out Lib Dems joining any coalition". BBC News. 2010-04-13.
- Ross, Tim (2012-07-23). "Clegg would form coalition with Labour after election". The Telegraph (London).
- Savage, Michael (2012-09-09). "Clegg Must Go for Lib-Lab coalition - Ed Balls". The Times (London).
- Tall, Stephen (2012/07/2012). "48% of Lib Dems would prefer coalition with Labour in 2015". LibDemVoice. Retrieved 29 December 2012.
- "National Assembly 2003 Election Results". BBC News. 2003-05-02. Retrieved 29 December 2012.
- "What happens in the event of no overall majority for any party?". National Assembly For Wales. Retrieved 29 December 2012.
- "Lib-Lab Constitutional Reform Committee Disbanded". BBC News. 2001-09-20. Retrieved 29 December 2012.