Liberal Democrat MP and chief secretary to the Treasury Danny Alexander, has ruled out any cuts to the top rate of income tax before next year's general election, saying this would only happen 'over my dead body' and opening up a split in views between the two coalition parties.

In an interview with the Daily Mirror Alexander said the 45p rate was the 'right place to be' and suggested he would veto any Conservative proposal to cut it to 40p before the election in mid 2015.

Alexander said: '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.'

Last week at prime minister's questions, David Cameron refused three times to rule out a reduction in the top rate of tax when pressed by the Labour leader Ed Miliband.

Cameron said: 'The fact is, under this government, the richest will pay more in income tax in every year than any year when you were in office. That is the truth.'

In a BBC radio interview this morning, London mayor Boris Johnson said it was inconceivable that the Conservatives would go into the next election without a pledge to lower the higher rate of tax.

Johnson said: 'The last thing I want to see is a pointless sacrifice from the Liberal Democrats, let alone the dead body of Danny Alexander. Sooner or later there will have to be a new Conservative manifesto and I can't believe we are going to go into an election on a campaign to keep our tax rates higher.'

'UK income tax is now higher than the average in the EU. That never used to be the case. I don't see why it should be the case for the long term and I see no reason why we shouldn't bring it down,' Johnson said.

When asked if this meant that the Conservatives would attempt to introduce a cut in the higher rate before the election, despite Alexander's pledge to keep the 45p rate till that date, Johnson replied: 'Who can say what will happen to Danny Alexander? Stranger things have happened at sea.'