High earners were dealt a double blow in the Budget, which raised the highest rate of income tax to 50 per cent and curbed the amount of tax relief they can claim on pension contributions.

In what accountants and advisers quickly dubbed the “Robin Hood Budget”, Alistair Darling risked an exodus of wealthy individuals from the UK as he introduced a punitive income tax regime for the highly-paid.

The government had previously planned to introduce a new income tax rate of 45 per cent on income over £150,000 from April 2011. But in an attempt to plug a gaping hole in the public finances, it has brought this increase forward by a year and raised the rate to 50 per cent. It also removed the personal allowance – the first £6,475 of earnings that are currently tax-free – for high earners and watered down tax breaks for wealthy pension savers.

“High earners are clearly going to be feeling under the cosh,” said Richard Mannion, national tax director at accountancy group Smith & Williamson. “There will be the loss of personal allowances from next year for those earning over £100,000 a year and a new higher rate of 50 per cent for those earning over £150,000, followed by a reduction in pension relief for those earning over £150,000 in 2011.”

In return for these higher taxes, the government announced a number of measures to help savers – including a £3,000 increase to the annual individual savings account (Isa) allowance – and tax credits to boost the incomes of lower earning pensioners and families.

Anyone earning more than £100,000 will face higher tax bills in less than a year’s time – with the worst hit those with earnings over £150,000. From April 6 2010 they will have to pay half of any earnings above that level in income tax and will also lose their tax-free personal allowance of £6,475.

Deloitte calculates that the combined effect of the new 50 per cent income tax rate and the loss of the personal allowance means that someone with an income of £250,000 will from next year have to pay £12,590 more in income tax.

When these income tax rises are combined with the previously announced increase to the rate of employees’ National Insurance, Ernst & Young calculates that, “the [top] rate would soar to 51.5 per cent, the sixth highest in the OECD”.

Then, from April 2011, anyone earning more than £150,000 will see their ability to claim income tax relief on pension contributions restricted.

“This goes way further than anyone expected,” said Jonathan Rice, associate partner at Deloitte, the accountancy firm. “For a long time, there has been an attack on higher rate taxpayers who, to an extent, are being held responsible for the financial woes of economy.”

Advisers felt these extra charges could be extreme enough to persuade the highest earners to leave the UK for other, more favourable, tax jurisdictions and to deter successful entrepreneurs from moving here.

“This might tip the balance for higher earners who had just about got used to a tax rate of 45 per cent, only to hear they will have to pay even more,” said Leonie Kerswill, tax partner at PwC. “It is likely this will encourage some people to leave the UK and work elsewhere.”

Income tax rises may also encourage companies to bump up or restructure the salaries and bonuses of executives this tax year.

“The higher taxes could speed the exodus of financial professionals to Geneva and Zurich which have laid out the welcome mat and are being touted as low-tax world financial centres,” said David Adams, head of residential at Chesterton Humberts, the estate agent.

Changes to the tax relief on pensions will also deter higher earners from saving, warn advisers.

At present, higher rate taxpayers can claim income tax relief of 40 per cent on pension contributions. But from 2011, people with income over £150,000 will be unable to claim the full higher rate relief. The government said the relief would be tapered down until it is capped at the basic rate of 20 per cent for anyone earning more than £180,000.

So, those earning £180,000 will only be able to claim back 20 per cent on pension contributions, even though they will have paid income tax of up to 50 per cent.

PwC calculates that someone earning enough to make the maximum pension contribution of £245,000 a year would miss out on £49,000 in tax relief when the new rules kick in.

They also face a double blow as full income tax will still be charged on any benefits taken from pensions in retirement, even though they have not benefited from the full relief.

“Removing this incentive to save, particularly at a time when economic circumstances have affected people’s views over the value of pension saving, sends completely the wrong message,” said Martin Palmer, head of corporate pensions marketing at Friends Provident.

“Higher earners will ultimately receive basic rate tax relief on the contributions they pay in but when they come to take their pension they will no doubt have to pay the higher rate of tax.”

Better news came for savers, who will be able to contribute more into tax-free Isas. The chancellor extended the Isa allowance from £7,200 to £10,200. Investors over the age of 50 can make use of the increased allowance from October 6 this year. All other savers will be able to from the start of the next tax year on April 6, 2010.

Up to half – £5,100 – of the enhanced Isa allowance can be used for cash savings, with the remainder open to other investments such as equities and bonds.

Other than the extension to Isas, investors received few incentives.

Investors willing to back higher-risk ventures through the enterprise investment scheme (EIS) will be allowed to “carry back” their entire investment to the previous tax year. Previously, investors could only carry back the 20 per cent tax relief allowed on EIS investments up to £50,000. Now, they can claim relief on up to £500,000.

But some advisers believed that investors’ behaviour, and their choice of schemes, would be more influenced by the increased gap between the 50 per cent rate of income tax and the 18 per cent rate of capital gains tax (CGT).

“This widens the gap between CGT and income tax,” said Richard Proctor at Grant Thornton. “I expect there will be new opportunities for investing in assets that produce capital gains.” Leonie Kerswill of PwC suggested wealthier investors would take a renewed interest in property. “It might encourage some to go into buy-to-let because you only get CGT at 18 per cent – especially if they think property prices have pretty much hit the bottom.”

First-time buyers and homeowners received little help. One of the measures aimed at stimulating the housing market was a three-month extension to the stamp duty holiday for properties worth £175,000 or less. But estate agents did not expect this to have much of an effect on the market.

More money was allocated to stimulate new housebuilding and support shared equity schemes, although this will only help low-income homebuyers looking to live in new-builds.