Vince Cable, one of the Liberal Democrats' most senior figures, has insisted that his party would not form a coalition unless it retained the same number of ministers as in the last parliament.
Senior rightwing Tories have been urging David Cameron to slash the number of Lib Dem ministers in any renewed deal following Thursday's general election to reflect an expected reduction in the party's seats at Westminster.
The business secretary's comments come as the prime minister's allies said he was preparing for coalition talks with the Lib Dems if the Tories won the most seats in a hung parliament.
Nick Clegg's party is expected to win around 25 to 30 seats compared with 57 in 2010 at the height of his popularity. But Mr Cable, speaking to the Financial Times in his Twickenham constituency, said that his party would not cut a deal with Labour or the Tories unless it had equivalent power to last time around.
For the past five years the party has had 24 ministers, of which seven were in the House of Lords and 17 in the House of Commons, meaning if Mr Cable's demands were met most Lib Dem MPs could be working at a ministerial level.
"There is no way we would accept a weaker role than the one that we have had in terms of policy or the number of ministerial jobs," he said.
Mr Cable said it was "grossly arrogant and presumptuous" of Tory cabinet ministers - understood to include Sajid Javid, Theresa May and Chris Grayling - to argue that the Lib Dems could be restricted to just 10 ministers in another coalition.
"Our vote may be a bit down on where we were last time, but so would [the Tories] be," said Mr Cable. "If that is the way they're thinking, it would present serious problems."
After five sometimes gruelling years, during which support for the Lib Dems has dropped from 24 per cent to single figures, the leadership faces difficulties in getting a new deal approved by its membership.
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Mr Cable said: "I think it would be very tough and they would obviously want us to consider our position very carefully but I don't rule it out."Senior Lib Dems have said they would potentially work with either the Tories or Labour. They claim that they would add "heart" to a Tory government and "brains" to a Labour one.
Mr Cable said it was easy to identify fundamental issues where his party disagreed with the Tories: for example public spending, Europe, Right to Buy and social housing.
"But they are transactional. With Labour there aren't major policy differences but there is a much more tribal outlook," he said.
Labour and the Lib Dems share common ground on taxation, deficit reduction, welfare and green energy - as well as opposing an EU referendum.
<>But Mr Clegg said last month that Labour had acted with "frothing bile" towards his party for forming a coalition with the Tories and he ruled out any deal with Ed Miliband's party that relied on "life support" from the Scottish National party.
A Lib Dem spokesman said the party supported Mr Cable's comments that the Lib Dems would not enter a coalition unless it was the right thing for the country. "But discussions on the details of future coalition policies and ministerial decisions are for after . . . Thursday."
The Tories have poured money and resources into toppling Mr Cable from Twickenham, a seat he has held since 1997 - currently with a majority of 12,000 - in what would be a remarkable coup if they succeeded.
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