Alistair Darling is expected to launch a fresh crackdown on tax avoidance in the Pre-Budget Report (PBR) in an attempt to ensure that high earners do not sidestep the new 50 per cent tax rate.

There has been disquiet among top earners over the new top rate of tax that will be charged on all income over £150,000 from April next year.

It is likely that the Chancellor will use the PBR, which is expected to take place in early December, to curb any measures wealthy individuals may make to cut their tax bills. The clampdown will also serve as a shot across the bows against bumper bankers’ bonuses.

The Government says that its high tax rate will raise nearly £3 billion by 2012, but there are fears among policymakers that the income may be reduced if higher earners reorganise their affairs so that less of their money is liable to income tax.

Research from the Institute of Fiscal Studies, a leading think-tank, showed that the wealthiest individuals were the quickest to react to tax changes.

The Government immediately closed one potential loophole by cutting the tax relief available on pension contributions from 40 per cent to 20 per cent for those earning more than £150,000.

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