MPs are debating whether the UK should ratify the Lisbon Treaty. Here is a timeline of events leading up to this.
18 June 2004: EU leaders agree a constitution, bringing together for the first time the many treaties and agreements on which the EU is based. It defines the powers of the EU, stating where it can and cannot act and where the member states retain their right of veto.
Spring 2005: Labour, the Conservatives and the Liberal Democrats all promise a referendum on whether to ratify the EU Constitution in their UK general election manifestos.
29 May: French voters decide not to ratify the constitution.
2 June: The Dutch electorate also rejects the constitution, effectively ending the project.
21 September: European Commission President Jose Manuel Barroso admits the EU will not have a constitution for "at least two or three years".
Early 2007: Work begins on a replacement treaty. Unlike the constitution, this would not overwrite all existing EU treaties and legislation but "amend" it. The government says this means a referendum is not needed. But critics say this argument is a legal nicety and that the substance of the reforms, on which a referendum was promised in the UK, remains the same.
18 June: Prime Minister Tony Blair says he will not sign a treaty giving up control of British law to Brussels. He adds that he will not compromise on the Charter of Fundamental Rights, foreign policy, common law, and tax and benefits. But the Conservatives say any deal that hands power to the EU must be put to the public in a referendum.
21 June 2007: EU leaders meet to discuss the main points of the EU Reform Treaty. Commission president Jose Manuel Barroso urges the UK not to hold a referendum.
19 October: EU leaders reach a deal on a treaty, which will be formally signed on 13 December.
30 October: Former French President Valery Giscard d'Estaing, an architect of the original constitution, says the treaty differs in "approach rather than content".
13 December: Prime Minister Gordon Brown signs the EU Treaty in Lisbon, arriving after other leaders take part in the official ceremony.
21 January: A House of Commons motion is passed to approve in principle the EU (Amendment) Bill, which would ratify the treaty.
28 January 2008: The government defeats a Conservative attempt to extend the Commons debate from 12 to 18 days. Ministers offer a "guarantee" that there will be enough time for scrutiny, but opposition MPs accuse the government of cynicism.
29 January: Commons debate day 1: Parliamentary debate on the content of the treaty gets under way, with the early focus on home affairs, justice and immigration matters. Meanwhile, millionaire Tory donor Stuart Wheeler announces a legal bid to force a referendum on the treaty.
30 January: Commons debate day 2: The government wins a Commons vote on the energy policy aspects of the treaty. But the Conservatives say this is like writing a "blank cheque to Brussels".
5 February: Commons debate day 3: Human rights aspects of treaty
6 February: Commons debate day 4: on aspects of treaty relating to single market
7 February: A UK Independence Party activist loses a court challenge to the government over its decision not to hold a referendum on the Lisbon Treaty.
8 February: Labour MP Andrew Slaughter clashes angrily with EU treaty referendum campaigner Derek Scott, accusing Mr Scott of fronting a "dishonest" marketing exercise for the Conservative Party.
8 February: Senior Labour MPs Frank Field and Kate Hoey pledge to continue campaigning for an EU treaty referendum, despite pressure from their party to stop.
12 February: UK Foreign Secretary David Miliband jokes that the European Union might "not be able to afford" Tony Blair as its first president, a position which will be recreated if member states ratify the Lisbon Treaty.
14 February: France has formally ratified the Lisbon Treaty, with its publication in the country's official journal.
20 February: Commons debate day 5: The EU Treaty will strengthen, not undermine British foreign policy, the UK's foreign secretary says.
25 February: Commons debate day 6: International Development Secretary Douglas Alexander argues that the Lisbon Treaty will help the EU tackle global poverty. His Tory counterpart Andrew Mitchell condemns Labour's Chief Whip Geoff Hoon, claiming that he is employing "terror tactics" against potential rebels.
26 February: Commons debate day 7: At the start of the debate on EU institutional reform, the Liberal Democrats stage a dramatic Commons walkout after the Speaker blocks debate on their bid to force a referendum on UK membership of the EU.
27 February: Commons debate day 8: Shortly after protesters clamber onto the House of Commons roof to voice their opposition to Heathrow expansion, MPs considered how the EU's policy on aviation squared with its stated aim of carbon emissions reduction.
29 February: Review of the week:
3 March: Commons debate day 9: The debate begins hours after two protesters scale a crane near Parliament. But two days before a crunch vote on the issue, Europe Minister Jim Murphy resists the calls, telling MPs: "The place to make these decisions is in this chamber - not on a crane half way above the city sky of London."
4 March: Commons debate day 10: The Liberal Democrats force a vote on whether there should be a debate and vote on their call for a referendum on the wider question of the UK's membership of the European Union. It is defeated by 471 votes to 68.
5 March: Commons debate day 11: MPs reject a Conservative call for a referendum on whether the Lisbon Treaty should be ratified by 63 votes.
11 March: Commons debate day 12: MPs vote by a majority of 140 to approve the EU (Amendment) Bill, which now goes to the House of Lords.
19 March: Polish PM Donald Tusk says a referendum may be necessary on the Lisbon Treaty because of a dispute with the opposition and President Kaczynski.
28 March: The Lisbon Treaty would have no major impact on UK sovereignty, says an influential committee of peers.
1 April: The Polish parliament has overwhelmingly backed the EU reform treaty, after weeks of argument.
9 April: Conservative hopes of forcing a referendum on the EU treaty have taken a further blow after Lib Dem peers said they would vote against one.
21 April: Millionaire Stuart Wheeler goes to the High Court to seek a judicial review of the government's refusal to hold an EU referendum.
24 April: The Danish parliament has approved the EU's Lisbon Treaty by a margin of 90-25, with a final stage of ratification by the Queen, while German MPs also backed the treaty.
2 May: Millionaire Stuart Wheeler has won his battle to force a High Court review into whether the government should hold a referendum on the Lisbon treaty.
21 May: Peers have rejected an attempt in the Lords to put into law a requirement that a referendum is held before Britain joins the euro.
4 June: The influential Irish Farmers' Association has thrown its support behind the EU's Lisbon Treaty ahead of a key referendum.
8 June: Ireland's PM Brian Cowen has launched a strong attack on opponents of a key EU reform treaty ahead of the country's referendum on the issue.
11 June: The judges hearing millionaire Stuart Wheeler's attempt to force a referendum on the EU Treaty have reserved their judgement after a two-day hearing.
11 June: Ireland's EU treaty No campaigners have recruited the country's most famous turkey to help secure crucial votes in this week's referendum.
11 June: The House of Lords has voted against holding a referendum on the EU Treaty - a day before the Irish Republic's national ballot on the agreement.
13 June: Voters in the Irish Republic have rejected the European Union's Lisbon treaty in a vote by 53.4% to 46.6%, a major blow to leaders in the 27-nation EU.
13 June: The euro has fallen against the dollar and the pound after Ireland rejected the EU's reform treaty in a referendum.
13 June: Foreign Secretary David Miliband says the UK must ratify the EU Treaty despite its rejection by Irish voters.
14 June: The BBC's Jonny Diamond asks where next for the EU Treaty following the Irish referendum result.
14 June: The Conservatives have called on the government to allow the British people to vote on the EU Treaty after it was rejected by Irish voters.
15 June: David Miliband has said there was no question of "bulldozing" Ireland into voting again on the EU Treaty - but Britain will continue to ratify it.
15 June: The EU must help find a solution on how to move forward after Ireland's rejection of the Lisbon Treaty, the Irish prime minister has said.
16 June: Irish Foreign Minister Micheal Martin has said it is "far too early" to seek a solution to the Irish rejection of a European Union reform treaty.
16 June: Gordon Brown has said EU leaders must agree to give Dublin "time to reflect" on its next steps over the EU treaty.
16 June: EU foreign ministers have agreed to keep the Lisbon reform treaty alive despite its rejection by Irish voters.
17 June: The European Union must not embark on drafting a new treaty after Irish voters rejected the Lisbon Treaty, France's Europe minister has said.
18 June: Conservative leader David Cameron has told Gordon Brown to show "backbone" and declare the EU treaty "dead".
18 June: The UK has effectively ratified the EU's reform treaty - despite the decision by Irish voters to reject it.
19 June: European Union leaders meeting in Brussels have refused to set a deadline for a deal on the stalled Lisbon Treaty after its rejection by the Irish.
19 June: An attempt to block Britain's ratification of the Lisbon Treaty has been rejected by the High Court.