The Liberal Democrats will go into the next general election making clear that some manifesto pledges are "dependent on circumstances", Nick Clegg has signalled.
The Deputy Prime Minister said the increasing likelihood of coalition government meant parties could no longer guarantee implementing their manifesto in full.
The comments, in a round of broadcast interviews at the Lib Dem conference in Brighton, came after Mr Clegg made a grovelling apology for breaking his promise to oppose hikes in tuition fees.
Asked whether there was now a fundamental problem with politicians making iron-clad commitments, the Lib Dem leader told Channel 4 News he thought there would have to be different levels of pledge in future.
He said: "If we are moving, as I believe we are, into a much more fluid political environment where the kind of old pendulum swing from the red team to the blue team is going to be much more difficult to predict ... I think all parties will need to be more upfront with the British people on what is kind of 'tablet of stone' stuff, and the others that will depend on circumstances."
Mr Clegg said the Lib Dems had been "ahead of the game" because they put the four policies they would "die in a ditch" for on the front page - the pupil premium, £10,000 tax-free allowance, banking reform and political reform.
"We said that is the stuff we really really care about, the other stuff is dependent on circumstances," he added.
Mr Clegg also fuelled confusion over whether he wanted to introduce means testing on some universal benefits, such as winter fuel payments, in 2015-16 - potentially a breach of the coalition agreement.
He began by insisting there was "no question" of such cuts during this parliament, because it would be against the "holy text" agreed with the Conservatives.
However, Mr Clegg went on: "My own view is that all parties will need to confront the simple irony, which is that we are giving free bus passes and TV licences and winter fuel payments to (entrepreneurs) Alan Sugar and Peter Stringfellow while limiting housing benefit to families on much lower incomes."