UK's ruling Labour Party rejects accusations of U.S. election interference

The U.K.'s ruling Labour Party has rejected accusations by former U.S. president Donald Trump's campaign team that the British party's members have interfered in the upcoming U.S. election.

Republican presidential nominee Donald Trump's campaign team on Monday accused the Labour Party of "blatant foreign interference" in the vote, after party volunteers travelled to several battleground states in the U.S. to help campaign for Democratic nominee and current Vice President Kamala Harris.

"It is common practice for campaigners of all political persuasions from around the world to volunteer in U.S. elections. Where Labour activists take part, they do so at their own expense, in accordance with the laws and rules," a Labour Party spokesperson said in emailed comments to CNBC.

The U.K.'s Prime Minister Keir Starmer also rejected accusations earlier on Wednesday during a visit to Samoa in the South Pacific.

"The Labour Party has volunteers, [they] have gone over pretty much every election," he said, according to the BBC.

"They're doing it in their spare time. They're doing it as volunteers. They're staying, I think, with other volunteers over there," he noted.

Asked if the row risked damaging his relationship with Donald Trump, the prime minister said "no," pointing to a dinner the two politicians enjoyed at Trump Tower in New York last month, the British public broadcaster reported.

Asked about the accusation in Parliament, Deputy Prime Minister Angela Rayner on Wednesday told lawmakers that "people in their own time often go and campaign and that's what we've seen, it happens in all political parties, people go and campaign and they do what they want to do with their own money."

On Monday, Trump's campaign team filed a complaint with the Federal Election Commission, claiming that the interference had taken the form of "apparent illegal foreign national contributions made by the Labour Party of the United Kingdom and accepted by Harris for President, the principal campaign committee of Vice President Kamala Harris."

It's against U.S. law for foreign nationals to directly or indirectly "make any contribution of money or other thing of value, or to promise expressly or impliedly to make any such contribution" in connection with U.S. elections, or for any person to solicit, accept, or receive any such contribution from a foreign national.

Calling for an investigation into the matter, Trump's team cited media reports by the Washington Post and Telegraph newspaper, suggesting that the center-left Labour Party had been "offering advice to Kamala Harris about how to earn back disaffected voters" and that "the Harris campaign has been ... generously borrowing language and themes from prominent Labour Party officials."

The letter then cited a since-deleted LinkedIn post in which Sofia Patel, the head of operations at Labour, said that nearly 100 current and former Labour Party staff members were heading out to North Carolina, Nevada, Pennsylvania and Virginia over the next few weeks to campaign ahead of the election on Nov.5. The party would "sort" housing for any volunteers making the trip, Patel said, according to a post caption featured by the Trump campaign's letter.

CNBC has reached out to the Labour Party for comment on the authenticity of the post.

"Those searching for foreign interference in our elections need to look no further than Ms. Patel's LinkedIn post," Trump's campaign team said, adding that "the interference is occurring in plain sight."

"Ms. Patel's posts and press reporting surrounding the relationship between the Harris campaign and the Labour Party create a reasonable inference that the Labour Party has made, and the Harris campaign has accepted, illegal foreign national contributions," the complaint said.