David Cameron has hit back at claims by Labour leader Ed Miliband that secretly taped comments by Vince Cable showed the coalition government was a "sham".
The PM accused Mr Miliband of "sniping from the sidelines" and insisted the coalition was working well.
He defended his decision not to sack the business secretary for saying he had "declared war" on Rupert Murdoch.
It comes as Labour tried to prevent Culture Secretary Jeremy Hunt taking on Mr Cable's regulatory powers.
Mr Cameron said: "Coalitions do have their difficulties. Coalitions do have tensions, even contradictions, that is a fact."
But he urged people to "look at the bigger picture", claiming the coalition was succeeding in its aims of cutting the deficit and reforming public services.
He said people wanted politicians to "put aside their personal differences to work together in the national interest and we are getting things done".
Asked about Mr Miliband's claim that the coalition was a "sham" and was in fact a Conservative government, Mr Cameron said: "I think he is wrong."
He said it was "delivering in terms of the real problems the country faces.
"Just sniping from the sidelines is not constructive," he added.
Meanwhile, shadow business secretary John Denham has questioned whether Jeremy Hunt is a "fit and proper" person to take on the regulatory role, as he had praised Mr Murdoch in the past.
Cabinet Secretary Sir Gus O'Donnell rejected Mr Denham's claims, saying the transfer in responsibility for media competition to the culture secretary was "precisely to ensure there was no conflict of interest" regarding Mr Cable.
But Mr Denham said he was not satisfied with the response from Britain's top civil servant, saying: "It is very hard to see how any decision Jeremy Hunt makes will enjoy complete confidence.
"What Labour has always asked for in this case is that both sides are given a fair hearing - and are seen to be given a fair hearing."
Mr Hunt was handed the power to arbitrate on Mr Murdoch's plan to take full control of broadcaster BSkyB, along with Mr Cable's responsibilities for media competition, after the business secretary's gaffe.
The row over comments by Lib Dem ministers taped by undercover Daily Telegraph reporters has been seized on by Labour as they attempt to paint the coalition as a Conservative-led administration, with the Lib Dems as mere "props".
"These are decisions of a Conservative-led government propped up by Liberal Democrat passengers. Passengers not in the front seat, not even in the back seat of the car, passengers who have got themselves locked in the boot," he told a news conference.
Mr Miliband was speaking at the launch of a scheme inviting young people to join Labour for a penny, in a recruitment drive designed to attract disillusioned former Lib Dem supporters.
He has said he would have sacked Vince Cable if he had been prime minister - but he also extended an olive branch to Lib Dem ministers unhappy with the government's direction, saying he would "welcome" them on the Labour benches.
But the row has been dismissed as a "storm in a teacup" by senior Lib Dems, with former leader Lord Steel saying similar complaints would have been heard if Labour ministers had been taped by undercover reporters.
And he said the row had "cheered up" Liberal Democrats, who have realised their colleagues in government are "fighting very hard".
He accused the Conservative-supporting Daily Telegraph of "trying to undermine the coalition" and said MPs would now be on their guard when talking to constituents which was a "very serious concern".
Nick Clegg denied Mr Cable had been spared the sack to prop up the coalition, telling BBC Radio Manchester the decision to strip him of his regulatory powers was "taken on the facts of the case" and he still had valuable work to do on issues such as apprenticeships as business secretary.
In the latest recordings to be made public, Scottish Secretary Michael Moore said cutting child benefit for higher-rate taxpayers was not "a fair thing to do".
Business Minister Ed Davey said he was "gobsmacked" by the child benefit decision, while Pensions Minister Steve Webb said he had complained about the policy.
And Transport minister Norman Baker said: "We've stopped Murdoch taking over BSkyB, or referred it to the competition authorities.
"That would have never happened under the Tories. They would have just said, 'Here you are Mr Murdoch, how much do you want?'"
Mr Moore insisted in an interview with BBC Scotland that his party was committed to the coalition government's five-year programme and that the Lib Dems as a party were in "robust, good health".