Andrew Grice: Restless backbenchers are a problem for all three party leaders

Inside Westminster

As the three main party leaders prepare to recharge their batteries during a three-week Commons Christmas break, they have more in common than they would care to admit.

The gulf between Nick Clegg and his MPs was thrust into the spotlight by the Liberal Democrats' anguished debate over university tuition fees. Less well-documented are the tensions between David Cameron and Ed Miliband and their own backbenchers.

The mood on the Conservative back benches is not as happy as it should be given that Mr Cameron has taken to the job of Prime Minister like a duck to water. The Tories have a respectable position in the opinion polls for a party that has announced deep spending cuts. Although the Coalition has ensured stable government, a surprisingly large number of Tory MPs don't like it. There is a growing chorus of complaints that too many concessions are being made to the Liberal Democrats – on crime, sentencing, immigration, the Human Rights Act and Europe.

And there are rising suspicions that Mr Cameron and Mr Clegg secretly plan for the Coalition to continue after the next general election, perhaps after they strike a voting pact.

Yesterday's attempt by Mr Cameron at the European leaders' summit in Brussels to rein in future EU spending was a nod to his backbench awkward squad. This week 27 of them voted against the Government on the Bill providing loans to Ireland but no one noticed because the Coalition enjoys an overall majority of 84. Without the Liberal Democrats' 57 MPs, the Cameron critics would enjoy immense power. So their frustration with the Coalition is huge.

The Prime Minister adopted diversionary tactics when he addressed the 1922 Committee of Tory backbenchers on Wednesday, responding to their grumbling about the new system of MPs' expenses by threatening to reform or even kill off the new-born Independent Parliamentary Standards Authority. He told his troops they should be proud of the Government's radical reforms of health, welfare and education (which are indeed more in tune with Tory than Liberal Democrat instincts). But there was a sting in the tail. "We must look after the Lib Dems," said Mr Cameron, revealing his fears for the plight of his friend Nick.

Labour is not in a coalition but Ed Miliband must sometimes feel as if he is. He started his job as Labour leader in September with a handicap: many of his MPs, and even his Shadow Cabinet, had backed his brother David for the post. Labour insiders say that, although he was confident of winning, Ed Miliband had not really prepared a proper plan for the aftermath (unlike his brother). Some Labour backbenchers accuse him of dither and delay and not sending enough signals about his direction of travel in his first 100 days. It is true that some of the sniping is from Blairites who are desperate to be proved right; they warned during Labour's leadership election that Ed was a ditherer. But not all of it.

Ed Miliband's allies insist he is getting his act together, citing his improved performance at Prime Minister's Questions. Although Mr Cameron "won" their Commons joust on Wednesday, Mr Miliband had the last laugh. BBC TV's evening news bulletins led with his claim that Mr Cameron would break his flagship election pledge to increase health spending every year on top of inflation.

This "same old Tories" label is potentially very damaging. It highlights the downside of the Coalition for Mr Cameron. Some Tories fret that if the Liberal Democrats are seen as the Tories' conscience – the people who put the "liberal" into the "liberal conservative" brand – then Mr Cameron might not complete his project to detoxify his party after all.

That is one reason why, for now, Mr Clegg rejects pressure from his restive backbench troops to trumpet more loudly his party's policy gains at the Tories' expense. He believes that doing so would portray an image of a divided, weak government, and undermine the Liberal Democrats' prospects of convincing voters they are a serious party which can govern responsibly rather than a "wasted vote" party for protest voters.

Whingeing by backbenchers is nothing new. Many of them wouldn't do it if they were frontbenchers. The three leaders are secure – for now. However, the fate of Margaret Thatcher, Iain Duncan Smith and Sir Menzies Campbell, all turfed out by their own party, reminds us that backbench rumblings can grow into something much more threatening. In 2011, all three leaders have much work to do in tending their own back garden.