Mr Clegg meets Mr Cameron privately on Saturday evening, after a day of talks between the negotiating teams for the Conservatives and the Lib Dems.
Mr Brown also speaks to Mr Clegg by phone. Reports Mr Brown lost his cool with Mr Clegg are denied by Labour. He offers the Lib Dems talks if no agreement is reached.
The Lib Dem leadership "endorses in full" Nick Clegg's decision to talk to the Conservatives first.
Lib Dem negotiator David Laws says talks have been "very positive" but does not clarify whether the Lib Dems would demand a referendum on changing the voting system as a condition of any deal.
Labour has already offered a referendum on changing the voting system.
Mr Clegg also meets his party's governing body, the federal executive, to discuss Mr Cameron's proposals. He needs the support of a majority of Lib Dem MPs and the executive to enter into any deal.
SUNDAY 9 MAY
Shadow Foreign Secretary William Hague: 'We will meet Lib Dems again'
Conservative and Liberal Democrat
are locked in talks again for six hours.
Mr Cameron and Mr Clegg meet for a second time to discuss forming a government after the talks between the parties.
Shadow foreign secretary William Hague says the negotiating teams agreed economic stability would be key to any agreement.
It also emerges Mr Clegg met Gordon Brown at the Foreign Office to discuss a potential deal.
Mr Brown sends an e-mail to party activists saying it has been his duty as prime minister "to resolve the situation".
Several Labour backbenchers call for the prime minister to step down.
MONDAY 10 MAY
Another day of negotiations begin between the Tories and Lib Dems. Lib Dem MPs meet Mr Clegg and want assurances on what the Tories are offering. They also urge him to keep talking to Labour too.
Gordon Brown is to step down as Labour leader
1700 BST: Mr Brown throws negotiations into turmoil when he announces
step down as Labour leader by September.
Talks between Labour and the Lib Dems then begin formally following his announcement.
The Conservatives react to Mr Brown's announcement by upping their offer to the Lib Dems on electoral reform to a promise of a referendum on changing the voting system. They offer a referendum on changing the voting method to the Alternative Vote (AV) system.
Labour offers to put the AV system into law and then hold a referendum asking voters to approve it.
Mr Clegg says progress has been made in talks with the Tories but that they had not "reached a comprehensive partnership agreement for a full Parliament" and it is the "responsible thing to do" to open negotiations with the Labour Party, while continuing talks with the Tories.
BBC political correspondent Iain Watson said some cabinet members are sceptical about the idea of a "progressive alliance" with the Lib Dems.
TUESDAY 11 MAY
David Cameron gave his first speech as prime minister outside 10 Downing Street
Mr Cameron says it's now "decision time" for the Liberal Democrats.
Ex- Conservative cabinet minister Sir Malcolm Rifkind says he was "very angry" to learn Mr Clegg's team had secretly been meeting Labour.
As negotiations continue, it becomes increasingly apparent talks between Labour and the Liberal Democrats have broken down.
Labour sources say the Lib Dems have unaffordable tax and spending commitments.
Mr Cameron meets Mr Clegg in private for an hour.
By the early evening a close ally of Mr Brown says Labour are close to conceding defeat in their efforts to strike a deal.
Several senior Labour figures warn against a coalition with the Lib Dems, including John Reid and David Blunkett. Cabinet minister Andy Burnham says Labour has to "respect the results of the general election and we can't get away from the fact that Labour didn't win".
After a day of more talks behind closed doors it appears a deal will soon be struck. Then the pace of events quickens when a lectern is put outside Downing Street in preparation for the prime minister to make a statement.
1930 BST: Mr Brown tenders his resignation to the Queen.
The Lib Dems are quick to say talks with Labour failed because "the Labour Party never took seriously the prospects of forming a progressive, reforming government".
Labour's Lord Mandelson says his party had been "up for" a deal, but the Lib Dems had "created so many barriers and obstacles that perhaps they thought their interests lay on the Tory side".
1937 BST: Even after Mr Brown has resigned a final agreement on the details of a coalition government has not been agreed. Shadow foreign secretary William Hague says the meeting with the Lib Dems had a "very positive atmosphere".
Minutes later outside Downing Street he says he aims to form "a proper and full coalition" with the Lib Dems.
As Mr Cameron takes calls of congratulation from President Barack Obama and German Chancellor Angela Merkel the Lib Dems are still meeting to discuss the deal with the Tories.
2300 BST: Mr Cameron is already beginning work on deciding his new cabinet, with Nick Clegg confirmed as deputy prime minister.
0000 BST: Following hours of talks the Lib Dem parliamentary party and its federal executive endorse the coalition agreement by the required three-quarters majority at a meeting that breaks up just after midnight.
WEDNESDAY 12 MAY
Nick Clegg and David Cameron shake hands on the doorstep of Number 10
Mr Cameron begins shaping his coalition
he welcomes his deputy Nick Clegg to Downing Street.
He says his "historic" Conservative-led coalition government will be united and provide "strong and stable" leadership. It is the first time the Conservatives and Liberal Democrats have a power-sharing deal at Westminster in what is the first coalition in the UK since the Second World War.
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