Danny Alexander has ratcheted up the coalition spat over the top rate of tax by insisting it will be cut to 40p "over my dead body".
The Liberal Democrat Chief Secretary to the Treasury made the comment as he dismissed calls from the Tory benches for a pre-election reduction.
David Cameron has fuelled speculation by repeatedly refusing to rule out a further trimming the current 45p rate for those earning over £150,000 a year. It fell from 50p last year.
But in an interview with the Daily Mirror, Mr Alexander said: "I think it is right at 45%. I wouldn't go to cutting below 45%.
"I would say that would happen over my dead body.
Asked about Mr Cameron's refusal to rule out cutting the top rate, he replied: "You'll have to ask them (the Tories) why they answer those questions in those ways.
"If you ask me would I cut the top rate below 45p the answer is 'no'. In this Parliament we will not allow that to happen."
Mr Alexander also had some praise for Labour's Ed Balls - amid questions over whether the Lib Dems could work with the party in a future coalition.
"I play cricket with Ed Balls. I have opened the bowling at Lords while he kept wicket behind the stumps and I have to say he didn't let anything past him. So I would endorse him as a wicket keeper," he said.