Britain is poised to suffer the world’s worst exodus of millionaires amid fears Labour will increase wealth taxes.

The number of UK millionaires is expected to shrink by 17pc between 2023 and 2028, according to Swiss investment bank UBS, which published its research just days after Sir Keir Starmer’s landslide victory. 

Its annual Global Wealth Report revealed that around 519,000 millionaires are expected to quit the UK over the period, which is the most pronounced drop of all the countries it tracks. 

This will take the country’s total tally to 2.5 million. 

The Netherlands is the only other country expected to post a decline, although its drop is much smaller at 4pc. 

By contrast, countries like Taiwan, Indonesia and Thailand are among those with the sharpest rises. 

The projection comes as Britain’s high earners fear a series of new wealth taxes under Labour, alongside a renewed crackdown on non-doms. 

However, Paul Donovan, chief economist at UBS Global, said the reasons for the drop went beyond just higher taxes.

Mr Donovan said: “There is a case of push and pull. Sanctions against Russia have caused a shift in population over time in this particular group. The non-dom status shift that the Conservative government implemented has had a small effect.”

He added: “And the non-indigenous millionaire population, which is constantly shifting, will be looking for low-tax locations all of the time. That is a function of pull factors in other countries like Dubai or Singapore.” 

Mr Donovan also highlighted that the UK has an outsized number of millionaires, ranking only behind the US and China.

Japan, France and Germany are projected to overtake the UK by 2028.