Vince Cable has held unprecedented and detailed talks with the top official at the Treasury about the Liberal Democrats' economic policies - and declared himself willing to serve as chancellor after the next election.

As Whitehall gears up for a possible hung parliament, Cable told the Observer that he had been questioned by Nicholas Macpherson, the Treasury's permanent secretary, about what the Lib Dems' demands would be in a coalition with Labour or the Tories.

Cable was unaware of such meetings having taken place with Lib Dem shadow chancellors before previous general elections. The talks were a sign that the Treasury was "taking seriously" the prospect of his party playing a leading role in economic policy in what could be the first hung parliament since 1974.

"He wanted to know what we attached priority to. He wanted to know what we felt strongly about," Cable said, adding that his ideas on tax and spending were well received. He didn't say to me: 'Yes, minister, but you can't do that'."

Cable, whose credibility has grown throughout the economic crisis, made clear that, if he was to be offered the chancellorship in a hung parliament, he would jump at the chance. He did not want to be "the most unpopular person in Britain" as public spending is slashed, he said, but added: "I wouldn't be in this business if I wasn't willing to take the responsibility if it was to come my way."