Prime Minister Sir Keir Starmer has played down the significance of alleged interference by the Labour Party in the US presidential election.
The Trump campaign has filed a complaint with the Federal Election Commission in Washington seeking an immediate investigation into alleged “blatant foreign interference”.
Sir Keir, who met Trump last month, said party staff going to the US to campaign for Democratic candidate Kamala Harris were volunteers “doing it in their spare time” and staying with other volunteers.
Environment Secretary Steve Reed told the BBC the Labour Party had not funded or organised their trips.
Sir Keir denied the row risked jeopardising his relationship with Trump.
Foreign nationals are permitted to volunteers in political campaigns in the US as long as they are not compensated, according to Federal Election Commission rules.
Labour Party sources are insisting no one has done anything wrong, but there is undeniable awkwardness around tension with Trump, who could be elected as president in a fortnight.
Labour officials have invested significant energy in trying to forge links with the Trump campaign, both in opposition and now in government, which could now be at risk.
The row was sparked by a now-deleted social media post from Labour’s head of operations, Sofia Patel, that she had about 100 current and former party staff heading to America before polling day.
The LinkedIn post said she had “ten spots available” for anyone willing to travel to North Carolina to campaign for Harris, adding “we will sort your housing”.
The ensuing complaint from the Trump campaign is both pointed and theatrical.
In a reference to US winning its war of independence nearly 250 years ago, it says: “When representatives of the British government previously sought to go door-to-door in America, it did not end well for them.”
The Trump campaign complaint to the commission flags that senior Labour Party staff attended the Democratic convention in Chicago and met Harris’s campaign team, naming Morgan McSweeney, the prime minister’s chief of staff, and Matthew Doyle, Downing Street director of communications.
Deborah Mattinson, Sir Keir’s former director of strategy, was also named as someone who travelled to Washington in September to brief Ms Harris’ presidential campaign on Labour’s election-winning approach.
Ms Mattinson no longer works for Labour.
Labour sources say McSweeney and Doyle went to the Democratic convention in their own time, and that the Democratic Party didn’t pay their travel or accommodation costs.
Accommodation appears to have been offered by fellow volunteers and the cost travel appears to have been paid by the volunteers themselves.
Sir Keir briefly addressed the issue during a flight to the Commonwealth Heads of Government Summit in Samoa in the South Pacific.
He told reporters: “The Labour Party has volunteers, [they] have gone over pretty much every election.
“They’re doing it in their spare time. They’re doing it as volunteers. They’re staying I think with other volunteers over there.”
Labour volunteers in US helping Harris ‘in spare time’, Keir Starmer says