George Osborne and Nick Clegg
George Osborne and Nick CleggReuters

That sound you can hear echoing around Westminster is the hull of the coalition government creaking and cracking under the strains of its own contradictions.

No sooner did chancellor George Osborne make an audacious pitch for the Labour vote by pledging to work for full employment than deputy prime minister Nick Clegg accused him of stealing Lib-Dem policies and being "too preoccupied" with the fortunes of the rich.

The latest intervention from the Liberal Democrat leader appeared to go further than the careful "differentiation strategy" both halves of the coalition have agreed to pursue in the runup to the general election.

This one betrayed some genuine anger from Clegg, maybe even some personal animosity towards Osborne, and appeared designed to create some real damage through its timing.

The deputy prime minister was well aware that Osborne was to deliver a significant speech aimed at underpinning his agenda-setting budget, capitalise on the improving economy and point to some sunny uplands after a Tory election victory.

In his speech, the chancellor declared: "Today I'm making a new commitment, a commitment to fight for full employment in Britain. Making jobs a central goal of our economic plan.

"There is no reason why Britain shouldn't aim to have the highest employment rate of any of the world's leading economies. To have more people working than any of the other countries in the G7 group. That's my ambition," he said.

Osborne's Full Employment Pledge - Will Labour React?IBTimes UK

He also deliberately distanced himself from the Thatcher era, saying: "unemployment is never a price worth paying" for economic recovery.

He went on to claim that government tax cuts for individuals and businesses had been the biggest "for a generation" in a clear signal there would be more to come under a Tory government.

It was a significant speech aimed at offering a less Thatcherite, more caring, face to the electorate while offering some hugely ambitious goals for the next Tory government.

In other words, it was a full-blown, general election campaigning speech.

But Clegg appeared eager to take the shine off Osborne's speech, saying he had stolen the Liberal Democrat policy of raising tax thresholds for the lowest-paid because the Tories had a problem with their image.

"They are trying to steal credit for it because they know it is a big popular progressive measure that benefits millions of people.

"And they know that they, as a party, have a problem in that they appear to be too preoccupied with the fortunes of those at the very top of society."

His words were a clear echo of Labour's attack that the government always stands up for the powerful, as evidenced by its tax cut for millionaires.

And it seemed to hammer another nail into the deal at the centre of coalition, that the two parties can work together "for the good of the country" yet, when it comes to campaigning, maintain and pursue different identities in a mature, respectful even positive manner.

It is unlikely the Tories will lose too much sleep over the assault, however. They are increasingly ignoring the Liberal Democrats, calculating they are not a great threat at the election and will almost certainly not be in a second coalition with them after it.

That, of course, is one of the things that seems to be getting under the deputy prime minister's skin.