"A Conservative Chancellor delivering his own speech". That was Chris Huhne's striking description of the government's autumn statement on the Today programme this morning. It was further evidence of what has become increasingly clear since Tuesday; that the demise of Osborne's pledge to eliminate the structural deficit in one parliament has dramatically heightened the tension between the coalition parties.

Both the Lib Dems and the Tories assumed that they would enter the next election having wiped the slate clean, free to offer their own post-austerity manifestos. But the failure of Osborne's plan means that this is now a distant dream. The Chancellor's new aim to eliminate the structural deficit by 2016-17 (a target that could well be missed) means several more years of pain.

The tension was evident on Tuesday's Newsnight when Danny Alexander unilaterally committed the Lib Dems to further spending cuts in the next parliament. The Chief Secretary to the Treasury declared: "so yes Liberal Democrats and Conservatives will work together in government to set out plans for those following two years". He made it sound as if the Tories and the Lib Dems would present a joint economic manifesto based on the next Spending Review.

Now, the inevitable backlash, led by Simon Hughes and Matthew Oakeshott, has begun. Hughes, the party's left-leaning deputy leader, commented:

All governments need to make spending plans for the longer term, but any spending plans from the government after 2015 can only be provisional and subject to the result of the general election ... The Liberal Democrats will fight the next election on an independent manifesto which will be developed through our internal democratic structures, and without any collaboration or agreement with other political parties.

While Oakeshott, Vince Cable's representative on earth, declared:

The coalition agreement is for five years not seven. It is very dangerous for the Liberal Democrats to go into the next election tied like a tin can to the tails of the Tories, rather than as an independent party capable of forming an alliance with whoever we and the electorate choose. In the economic circumstances of the 20s and 30s, the Tories proved themselves to be past masters at swallowing up other parties. It would be very foolish if we were to make the same mistake again.

It's a debate that is likely to run until the date of the next election. But for now, it's clear that the coalition has entered a new, more dangerous phase.