The Prime Minister attempted to play down reports of deep divisions within the coalition over his controversial decision to veto a new European treaty, saying it was not surprising that Tories and Liberal Democrats "don't always agree about Europe".
David Cameron told the Commons he was unrepentant about his decision not to sign up to the deal in Brussels last week, claiming he was "standing up for Britain".
But Labour leader Ed Miliband used the final Prime Minister's Question Time before Christmas to urge Mr Cameron to return to the negotiating table and strike a better deal for Britain following the "catastrophic mistake" in the Belgian capital.
Mr Cameron was flanked by Nick Clegg as the pair attempted to draw a line under the ongoing dispute, which last night saw all 57 Lib Dem MPs including the Deputy Prime Minister refuse to take part in a vote endorsing the use of the veto.
Mr Miliband quoted Mr Cameron's new year message for 2011 in which he said "coalition politics is not always straightforward" but promised "a more collegiate approach".
He asked: "What's gone wrong?"
The Prime Minister said: "No one in this House is going to be surprised that Conservatives and Liberal Democrats don't always agree about Europe.
"But let me reassure you: you shouldn't believe everything you read in the papers."
Then, in a dig at Mr Miliband's relationship with his elder brother David, Mr Cameron said: "It's not that bad, I mean, it's not like we're brothers or anything."
He said Mr Miliband had "certainly walked into that one".
The Labour leader joked: "I think our sympathy is with the Deputy Prime Minister: his partner goes on a business trip, he is left waiting by the phone and he hears nothing until a rambling phone call at 4am confessing to a terrible mistake."
Mr Miliband asked how the Prime Minister was going to "pick up the pieces of the bad deal he delivered for Britain" following the veto.
"In the cold light of day, with other countries spending the weeks and months ahead trying to see if they can get a better deal for themselves, isn't the sensible thing for you to do to re-enter the negotiations and try and get a better deal for Britain?"
Mr Cameron told him: "I make no apologies for standing up for Britain. In the last few days we've read a lot about my opinions, we've read a lot about the Deputy Prime Minister's opinions.
"The one thing we don't know is what would you have done."
Mr Miliband said: "There was a better deal for Britain that you should have got and that is what the Deputy Prime Minister himself says."
He said the situation in Brussels and rising unemployment showed: "This Prime Minister thinks he is born to rule, the truth is he is just not very good at it."
Mr Cameron dismissed the attack as "recycled from a previous PMQs" and returned to the issue of whether Mr Miliband would have signed the treaty in Brussels.
Having previously indicated he would not have signed, "today I think the answer is maybe", Mr Cameron said.
"This leader of the Labour Party makes weakness and indecision an art form, that is a fact."
Summing up Mr Miliband's 2011, he said: "You told us at the start of the year in your new year's message 'the fightback starts in Scotland'. Well that went well, didn't it?
"You told us you would have credible plans to cut the deficit, we still haven't seen them.
"You said you would stand up to vested interests and yet you backed the biggest strike for years.
"We all know that you have achieved one thing: you have completely united your party.
"Every single one of them has asked Santa for the same thing: a new leader for Christmas."
Labour MP Thomas Docherty (Dunfermline and West Fife) asked Mr Cameron why Lib Dems abstained in yesterday's Commons' vote.
Mr Cameron said: "Last night there was something of a Parliamentary rarity which was a motion put down by an opposition party praising the Prime Minister - I'm very grateful to colleagues in the Democratic Unionist (party).
"I suspect many people concluded Labour simply wouldn't get their act together, it wasn't worth voting and as a result we won very easily."