The UK is set to lose the greatest proportion of millionaires as a share of population over the course of the current parliament, research from the Adam Smith Institute (ASI) has forecast.

The think tank predicted that the share of the UK population who are millionaires would fall by 20 per cent by 2028.

Currently, 4.55 per cent of British residents are millionaires, but the ASI has forecast that this will decline to 3.6 per cent by 2028.

It described the UK losing proportionally more millionaires than China or Russia as a “worrying indicator of our economic health and growth prospects”, noting that may millionaires were wealth creators who also pay a significant share of taxation.

The ASI attributed the exodus to several factors, including: High levels of current taxation; threats of further increases; a “hostile culture” towards wealth creators; and the abolition of the non-dom regime.

The other countries in the analysis forecast to see a decline in the proportion of millionaires were the Netherlands (-5 per cent) and the United Arab Emirates (-3 per cent).

To alleviate these concerns, the ASI urged the government to make the tax environment more welcoming to wealth creators.

In particular, it called for the abolition of inheritance tax, cuts to capital gains tax, and an international competitiveness assessment on the UK’s tax and regulatory treatment of non-doms and high net worth individuals (HNWI).

Commenting on the findings, former Chancellor of the Exchequer and former Conservative Party MP, Nadhim Zahawi, said: “The rate at which millionaires are leaving the UK is a vote of no confidence in both our current tax and regulatory regime, and anti-business and anti-prosperity measures that could be coming down the line.

“These individuals are often entrepreneurs and business owners. Their exit won’t just reduce necessary funds for public services - it will decrease investment in the wider economy too.

“I urge the government to rule out anything in the Autumn Budget on the 30 October that could drive them away even more.

“They should instead be focusing on attracting more millionaires from across the world to make a home and set up shop in Britain. Abandoning anti-non-dom policies and abolishing or cutting anti-wealth taxes would be a vital first step.”

ASI director of research, Maxwell Marlow, added: “These findings should be a wake-up call to the government. The more millionaires who leave the UK, the worse the impact on the economy will be.

“It’s important to understand that HNWIs aren’t only leaving in response to the UK’s uncompetitive tax and regulatory regime, the proposed abolition of the non-dom status, and the threat of increased taxation. They are understandably also reacting to a culture that is increasingly hostile to wealth creators.

“As long as we continue along this path, we can hardly be surprised that so many millionaires want to leave.

“This trend is not set in stone. We need to take a comprehensive review of our tax and regulatory treatment of millionaires and reconfigure it to attract more of them to our shores, as well as creating more of them at home.”

In its analysis, the ASI used data from New World Wealth and UBS/Credit Suisse wealth reports, as well as national data office population data and forecasts, for each respective nation.

It then calculated the number of millionaires within the country per capita and, using UBS/Credit Suisse forecasts for millionaires in 2028 against population forecasts provided by the ONS, and sought to calculate the predicted exodus of millionaires.

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