Britain's populist Reform UK party has unveiled plans to offer wealthy, often foreign newcomers a "Britannia Card" to gain exemption from tax on international wealth, income or gains for 10 years for a one-off, £250,000 ($336,000) payment.

The policy draws a new battle line before the next national election with Britain's governing Labour Party. The government has closed exemptions on so-called "non-doms", or non-domiciled residents, who have long paid little or no UK tax on money earned overseas.

Using a press conference to also criticise the opposition Conservative Party for hiking taxes on voters when it held power, Farage said the change would see the 250,000-pound payments distributed among Britain's lowest-earning 10% of full-time workers.

"We want, as a party, as many entrepreneurs, as many risk takers, as many job creators, as many people paying lots of tax, as many people investing huge sums of money - we want as many of them as possible to be in our country and that is why today we are coming up with this idea of the Britannia card," said Farage.

Last year some 10,800 wealthy people, some non-doms and some British, left the country, he said.

"We are also doing something with a very specific aim, aimed at those in work ... So making that gap between being on benefits and going to work bigger, this policy will directly contribute towards that."

Britain has not published official data on the number of millionaires leaving the country.

Reform UK is running ahead of Labour and the Conservatives in the polls before the next election, which must be held by the middle of 2029, buoyed by growing dissatisfaction with mainstream politics and a shift towards its brand of populism.

Responding to the policy, British finance minister Rachel Reeves told reporters that Reform had announced a "tax cut for foreign billionaires".

Responding to the policy, Chancellor of the Exchequer Rachel Reeves told reporters Reform had announced a "tax cut for foreign billionaires".

"That would mean either taxes on ordinary working people would have to go up to compensate for those lack of revenues, or ... Reform would have to cut public services," she said.