Republican presidential nominee and former U.S. President Donald Trump attends a roundtable discussion with Latino community leaders in Doral, Florida, U.S. October 22, 2024. / REUTERS/Carlos Barria/File Photo

Donald Trump's campaign has accused British Prime Minister Keir Starmer's Labour Party of "blatant foreign interference" in the U.S. presidential election after some volunteers travelled to help campaign for Vice President Kamala Harris.

The Republican candidate's camp has filed a complaint with the Federal Election Commission in Washington, calling for an investigation into what it termed apparently illegal contributions from Labour to the Harris campaign.

British political activists have long travelled to the U.S. ahead of elections, with those from the centre-left Labour Party typically supporting the Democrats, its sister party, and Conservatives and the right-wing Reform backing the Republicans.

Labour leader Starmer denied that the complaint would damage relations with Trump if the former president wins again on Nov. 5, saying Labour supporters were volunteering in their own time.

But the complaint is a potential complication as Trump is already close to Britain's right-wing politician Nigel Farage and former prime minister Boris Johnson, both of whom are critical of Starmer.

The British prime minister met Trump at Trump Tower in September in a bid to build a relationship ahead of the vote.

"I write on behalf of Donald J. Trump for President 2024, Inc. to request an immediate investigation into blatant foreign interference in the 2024 Presidential Election in the form of apparent illegal foreign national contributions," the complaint said.

British officials, who asked not to be named, told Reuters that some senior Labour advisers travelled to meet Democrat strategists in recent months, on the back of their landslide victory in the British election in July.

One topic they discussed was how Labour won back almost all the former industrialised areas that abandoned them in 2019.

Reform leader Farage, the right-wing politician who was instrumental in Britain's vote to leave the European Union, has also campaigned in the U.S. for Trump this year. Former British prime minister, Liz Truss, from the Conservative Party, also attended the Republican convention and denounced President Joe Biden as weak.

RULES ON FOREIGNERS

According to U.S. rules, foreigners can volunteer on election campaigns but cannot make financial contributions, and the allegations of interference will hinge on whether Labour covered any activists' costs.

The FEC previously fined the campaign of Bernie Sanders after Australia's Labour Party funded the flights and food of its volunteers to travel to the U.S. and support his campaign.

The Trump complaint cited media reports and a now deleted LinkedIn post from Sofia Patel, head of operations at Britain's Labour Party, who wrote that nearly 100 current and former Labour party staff would be travelling to the U.S. in the coming weeks to help elect Harris, a Democrat.

Patel's post had said she had 10 spots to fill in North Carolina, adding "we will sort your housing".

Labour said in a statement that any party members taking part would be doing so at their own expense. Volunteers were put up by other local supporters. Starmer said they were there in their spare time.

British political activists have a history of trying to be involved in U.S. politics.

A 2004 effort by the left-leaning Guardian newspaper to get Britons to write to American voters in Clark County, to urge them to vote against George Bush, appeared to backfire when it recorded a swing towards Bush.

Greg Swenson, the chairman of Republican Overseas UK, said while campaigners had always travelled from Britain to support the two main parties, he said Labour had drawn attention by talking about it so publicly.

"The issue here is it looks organised," he told Reuters. "It is really amazing that they have been so blatant about it."

Trump has also long engaged in rhetorical reversals, accusing his political rivals of engaging in the sort of behaviour that he has been criticised for.

He regularly describes Harris' replacement of President Joe Biden at the top of the Democratic ticket as a "coup," mirroring the way some critics described his supporters' Jan. 6, 2021 assault on the U.S. Capitol.

And in 2019 he called into a British radio show held by Farage ahead of an election, praising the then prime minister Johnson and criticising his rival, drawing accusations of electoral interference.