The UK has so far experienced just 40 per cent of cuts in public spending planned by George Osborne, with the majority still to come, says an influential economics think tank.

The Institute for Fiscal Studies (IFS) says the chancellor’s plans for fiscal consolidation up to 2018-19 implies a nine per cent drop in spending on the NHS, for example, as average spending per person drops by 2.4 per cent between 2010 and 2018.

But the report also said forcing the UK’s highest earners to contribute more could put the government’s long term finances at risk.

It pointed out that the share paid by the top one per cent of earners rose from 11 per cent in 1979 to 27.5 per cent in 2011-12.

Tax paid by the richest 300,000 residents accounts for 7.5 per cent of total income tax take, it said, not to mention disproportionately large contributions of VAT and capital taxes.

The Telegraph reported the IFS as saying, “lumping more taxes on the rich”, was not a sustainable long-term strategy.

Very wealthy people have several options to avoid tax, including relocating their wealth (or themselves), paying accountants to find tax loopholes or simply allowing fortunes to reduce.