Finance officials in Washington are warning that Britain may be close to 'peak taxation' and that any attempts by Chancellor Rachel Reeves to impose new levies would be futile and would threaten productivity and growth.

The International Monetary Fund (IMF) revealed last week that tax revenues as a percentage of Britain's total output would climb by 4.5 percentage points between 2024 and 2031 and could reach a post-Second World War-high of more than 40 per cent by the next decade.

It comes after Labour imposed an eyewatering £75 billion of new taxes on businesses and households since it took office in July 2024, with Britain experiencing the largest tax increase among the G7 most advanced economies, with France ranking second.

But senior officials monitoring the UK economy are understood to be concerned that the tax onslaught has gone too far.

They warned that the way UK taxes are levied is holding back economic growth.

In particular, they highlighted the Government's decision to freeze the thresholds at which people begin paying higher rates of income tax, arguing this is creating serious distortions in the system.

One example is that those earning between £100,000 and £125,140 a year face a 60 per cent effective tax rate, despite the top rate of income tax officially being 45 per cent.

Officials also believe the total level of taxation is out of hand. As a result, the Government's target of making Britain the fastest growing G7 economy was becoming impossible to deliver.

Some feared Britain was suffering a 'Laffer Curve' effect, the name given to when high taxes become a disincentive to work and thus total tax receipts actually decline. 

It is named after Californian economist Arthur Laffer, whose theory that high taxes discourage enterprise was embraced by President Ronald Reagan in the 1980s.

Labour's tax hikes have already resulted in thousands of better off people fleeing to lower tax jurisdictions such as Italy, Monaco, and Dubai, although some have since returned from the latter following the outbreak of the conflict in the Middle East.

And now, officials in Washington believe the Chancellor's tax policies have become an unacceptable burden, meaning that if the Government wanted to spend more on areas such as defence, it would be forced to cut public spending elsewhere rather than consider further hikes.

The warnings will cap a relatively gloomy week for the UK at the hands of the IMF.

In its latest economic outlook, the Fund cut its 2026 GDP growth forecasts for Britain to 0.8 per cent from 1.3 per cent, the largest downgrade of any of the G7 nations.