Chancellor Alistair Darling's Budget hit top earners with a new 50p income tax rate and the withdrawal of personal allowances.
The move broke Labour's 2005 General Election manifesto pledge which said: "We will not raise the basic or top rates of income tax in the next parliament."
Mr Darling increased the 45p top rate he announced in his Pre-Budget Report in November even before it had been introduced - and said the new 50% tax band would be brought in for those earning more than £150,000 a year early, from next April.
That means the rise will almost certainly take effect before voters go the polls to choose the next government.
The Chancellor also said he would tighten the screw on high earners further by amending plans he announced in the PBR to gradually reduce the income tax personal allowance for those on salaries of more than £100,000 a year.
Mr Darling said he would now "fully withdraw" the benefit of the personal allowance from next April.
Chief Secretary to the Treasury Yvette Cooper defended the 50p move as the right response to "exceptional circumstances".
Asked whether the hike represented a breach of the manifesto commitment, Ms Cooper told Sky News: "Well, it is. We never expected that we would have this kind of .....continued below
Advertisement starts
Advertisement ends
global financial crisis on a scale not seen for almost a century."In those circumstances, what we need to do is to make sure we are being fair. This is the right to be fair.
"Those on more than £150,000, we are talking about the highest-earning 1% in the country, and that's often a group that have actually seen the biggest gains, the biggest increases in their salaries over the last few years.
"That's why I think it's right to ask them to pay more at a time when we do need to make sure that the public finances are sustainable and we can sustain expenditure on health and education."
Sean Drury, international mobility partner at PricewaterhouseCoopers, said: "This is an unwelcome challenge to competing effectively.
"From next April, a year earlier than expected, the UK will rank 18th among the G20 economies in terms of income tax and social security rates for senior executives, based on current rates.
"The change applies to both domestic and overseas high earners working in the UK.
"This increased tax take could accelerate the movement of high earners and top performers in industries like finance and technology to other established and growing economic hubs.
"Countries like Switzerland will look increasingly attractive to some of the people in the key industries needed to lead the UK out of the recession.
"Companies relying on expatriates earning over £150k in the UK will face significantly increased employment costs - they will now pay £1 in tax for every £1 spent on providing essential benefits, such as housing and cost of living allowances."
