British Prime Minister David Cameron brushed aside calls on Wednesday to renegotiate an EU treaty, as his deputy premier’s appearance beside him in parliament cooled talk of a coalition rift.Conservative leader Cameron said he “made no apologies” for vetoing a new treaty at a eurozone crisis summit last week, a move which led to the other 26 European Union nations making an agreement without Britain.Deputy Prime Minister Nick Clegg of the pro-Europe Liberal Democrats stayed away on Monday when Cameron made a statement to lawmakers on the issue, but he was by his side at prime minister’s weekly questions on Wednesday.Cameron’s comments came a day after European Commission chief Jose Manuel Barroso said that Britain’s demands for its financial services industry to be exempted from EU regulation threatened to break up the single market.At a raucous final session before the Christmas break, opposition Labour leader Ed Miliband said it was the “sensible thing for him (Cameron) to do to re-enter the negotiations and try to get a better deal for Britain.”“I make no apologies for standing up for Britain,” Cameron replied.The two party leaders also traded barbs about the state of the 19-month-old coalition after Clegg stayed away on Monday and said at the weekend that Cameron’s actions were “bad for Britain.”“Let me say it’s good to see the deputy prime minister back in the house,” Miliband said, to laughter from MPs.Cameron hit back, saying that there would always be disagreements in a coalition and “no one in this house is going to be surprised that Conservatives and Liberal Democrats perhaps don’t always agree about Europe.”“It’s not that bad, I mean, it’s not like we’re brothers or anything,” he joked, referring to Ed Miliband’s battle last year with his brother, former foreign secretary David Miliband, for the Labour leadership.Clegg earlier told members of pro-single market group Business For New Europe (BNE) that the government is “absolutely determined” to ensure that Britain remains at the heart of the European single market.Clegg insisted he spoke for the whole government in asserting the need for Britain to “re-engage” with Europe.He told Liberal Democrat MPs and peers on Tuesday night the row would not bring the Coalition to an end.“The government will carry on until 2015. Full stop,” he said.However, Liberal Democrat ministers criticised Cameron’s negotiating tactics during a heated cabinet discussion the previous night. Chris Huhne, the Liberal Democrat Climate Change Secretary, complained that his party should have been consulted during the talks in Brussels which ended with Britain in a minority of one last Friday. He contrasted Cameron’s approach with his own during the global climate change talks in Durban, saying he cleared his lines with other ministers as the meeting progressedHuhne, a former MEP, is said to have interrupted the prime minister twice as he summed up yesterday’s 50-minute cabinet debate, protesting that Cameron had not addressed his points directly.Huhne went public with his criticism of Cameron. “Isolation is not a good posture in any negotiation,” he said.“Playing ‘Billy No Mates’ is no fun and is not effective in defending British interests.” He warned: “Businesses [abroad] need to know that we have influence in delivering the single market.“If they feel, sitting in a boardroom in Shanghai, that we don’t have influence then it is very likely they will be less attracted to investing here.”Other Liberal Democrat ministers – Clegg, Danny Alexander and Michael Moore – told the cabinet they were unhappy that Cameron had wielded the veto to block an EU-wide treaty aimed at rescuing the single currency.Vince Cable, the Business Secretary, is understood to have expressed concern about the possible impact on business and foreign investment in Britain if the country is viewed as not fully committed to the EU.