The number of people paying income tax at 40% or above will reach 7.8 million by 2027/28, according to research published by the Institute for Fiscal Studies (IFS).

This represents one in five taxpayers and one in seven of the adult population – a near-quadrupling of the share of adults paying higher rates since the early 1990s, the IFS said.

It stated that the six-year freeze to income tax allowances and thresholds which started in April last year is set to become the single biggest tax-raising measure since Geoffrey Howe doubled VAT in 1979.

Isaac Delestre, Research Economist at the IFS, said:

'For income tax, the story of the last 30 years has been one of higher-rate tax going from being something reserved for only the very richest to something that a much larger proportion of adults can expect to encounter.

'The freeze to thresholds is supercharging that process, pulling an additional 2.5 million more people into paying rates of 40% or more by 2027/28. Whether or not the scope of these higher rates should be expanded is a political choice as much as an economic one, but achieving it with a freeze leaves the income tax system hostage to the vagaries of inflation – the higher inflation turns out to be, the bigger impact the freeze will have.'