More than 6,000 millionaires will flee Britain for the European Union by the end of December to avoid a Labour tax grab, research shows.

A report by investment advisory firm Henley & Partners found 68pc of Britain’s wealthiest residents who plan to leave the country will vacate to Europe.

The most favoured destinations include: Italy, Malta, Greece, Portugal, Switzerland, Monaco, Cyprus, France, Spain and the Netherlands.

The firm estimates 9,500 high-net-worth individuals will leave the country before the end of the year.

The exodus will include 85 centi-millionaires – those with a net worth of over £100m – and 10 billionaires, according to the research collated over nine months and co-authored with wealth intelligence firm New World Wealth.

Their departure will have a knock-on effect on the economy, researchers warned.

Andrew Amoils, of New World Wealth, said: “The businesses they start up have a significant positive spillover effect on the middle class as they create large numbers of well-paying jobs in their base country.”

The UK will also lose more than 800 wealthy individuals to the United Arab Emirates; 720 to the United States; 300 to Australasian countries and 250 to Caribbean nations.

Rachel Reeves has vowed to end the UK’s non-domiciled tax regime after Jeremy Hunt, the former chancellor, increased tax on non-doms earlier in the year.

The special tax rules have historically provided valuable tax exemptions on worldwide income and assets of people who are resident in the UK but not considered permanently settled here.

Scrapping the status would cost the country £6.5bn and wipe out 23,000 jobs over the next six years due to lost investment, think tank Adam Smith Institute recently warned.

Now fears that inheritance and capital gains tax will rise at the Budget next Wednesday have caused even more wealthy Britons to rush for the door, Henley said.

Stuart Wakeling, of Henley & Partners, said: “It’s clear that next year’s increase in tax for non-domiciled individuals, announced by the previous Conservative government in March, prompted people to start considering leaving.

“This had a domino effect on UK nationals when they realised that capital gains and inheritance tax were the last ones remaining that could possibly be changed and make a difference to the Budget shortfall.”

The Chancellor has said she must raise taxes to fill a fiscal “black hole” of as much as £40bn at Labour’s first major fiscal statement next month.

The shortfall in the national finances has been disputed by experts and enlarged several times by the Government, which signed off on bumper public-sector pay rises shortly after entering office in the summer.