Mr Johnson said the tax rise sends out the wrong signals to entrepreneurs
Mayor of London Boris Johnson has warned that British enterprise will suffer if high earners are made to pay more tax.
The government is planning to raise the top level of income tax to 45%, and the Conservatives have indicated they will not reverse the increase, if elected.
Mr Johnson told BBC Radio 4's Any Questions? that "clobbering the rich" would stifle the City's potential.
The 45% rate will apply to earnings over £150,000 from 2011.
It was announced in November's pre-budget report by Chancellor Alistair Darling, along with a 0.5% rise in National Insurance contributions.
Tory mayor Mr Johnson said: "It sends out a signal to people who create wealth, people who are energetic... can generate new industries or drive large enterprises of one kind or another... that we want to take more of their proceeds away than before.
"It is a deterrent to enterprise."
Shadow Chancellor George Osborne told the BBC that raising the top rate would be "difficult to avoid".
Lib Dem Treasury spokesman Vince Cable has said high earners will simply avoid the high rate by declaring income as capital gains, taxed at 18%. He has called for a shake-up to make the tax system fairer.