Mr Trump’s key advisers are also debating whether to put Sir Keir Starmer, pictured, ‘at the back of the queue’ of world leaders invited to Washington after tomorrow’s inauguration

A senior source in Mr Farage’s, right, Reform UK, which is neck-and-neck with Labour in the polls, said: ‘We have a deep relationship with the Trump team and talk on a daily basis’

The timing of any official US visit by Sir Keir will be compared to that of Theresa May, who arrived at the White House as Prime Minister just seven days after Mr Trump’s first inauguration.

Government sources insisted last night that ‘constructive’ discussions with the incoming administration were under way over when Sir Keir could visit Washington.

Mr Trump’s campaign filed a Federal Election Commission complaint against Labour in October, accusing it of ‘blatant foreign interference’ after the party’s head of operations, Sofia Patel, asked for people to travel to the US to campaign for Harris.

A Trump ally told The Mail on Sunday: ‘It was election interference, plain and simple. Who the f*** do these people think they are?

‘Trump’s view is it’s none of their business what is going on here and they should have kept out.

‘How could their meddling possibly achieve anything? It didn’t. But it’s left a nasty taste in the mouth as far as President Trump and his team goes.

‘What a f***ing cheek these people have. And it didn’t do any good because Kamala was useless and clearly so were they.’

Meanwhile, a member of the Trump team told The Independent it was still not certain that the incoming President would accept Lord Mandelson as ambassador.

The new administration could further humiliate Sir Keir by rejecting Lord Mandelson’s, pictured, appointment as Britain’s ambassador to the US

Concerns about the Labour grandee’s perceived links to China were said to be partly to blame.

Mr Trump’s swearing-in tomorrow, which has been moved indoors due to icy weather, will be attended by Mr Farage, along with former Prime Ministers Liz Truss and Boris Johnson.

Despite the tensions, Sir Keir told the Financial Times he was building a ‘constructive’ relationship with Mr Trump, which he hoped would exempt the UK from threatened punitive trade tariffs and drown out the vitriolic attacks on him by Elon Musk, the world’s richest man and a member of Mr Trump’s team.

The Trump ally told this newspaper there had been ‘some chat’ that Sir Keir wanted a meeting in Washington as early as next month, but said: ‘That’s not Donald’s priority.

‘I tell you who he has been talking about – Prince William. He enjoyed their meeting in France [at the re-opening of Notre Dame] and Donald would like another state visit to the UK. He is talking about going through Palace channels.

‘Of course that isn’t how these things are traditionally set up but Donald doesn’t think traditionally.

‘Keir needs to put his big-boy pants on and realise that dealing with Donald isn’t like dealing with anyone else.

Concerns about the Labour grandee’s perceived links to China were said to be partly to blame. Picture: Chinese Vice Premier He Lifeng and  Chancellor Rachel Reeves

The Trump ally told this newspaper: ‘Donald expects you to kiss the ring. This time around, the President knows what he is doing and who his friends are’

‘Donald expects you to kiss the ring. This time around, the President knows what he is doing and who his friends are.

‘First time around there were clingers on, disingenuous people trying to get alongside for nefarious means.

People like Nigel Farage have proved their loyalty. Liz Truss has been over here several times and the President rates her highly.

Of course, he loves Boris. He makes him laugh. Boris is an alpha male like Donald.’

Speaking brutally about Sir Keir, the Trump ally said: ‘No one here knows who he is and, frankly, no one cares. Keir who? Ask most Americans in the street and they’ve no idea who he is.

‘President Trump has excellent UK contacts and he knows he can move through non-diplomatic and non-traditional routes and that suits him just fine.

‘He doesn’t need Starmer and doesn’t care about him. The guy is irrelevant. He will come at some point, of course, but the optics are more important to your guy than they are to Trump.’

A Downing Street insider insisted: ‘I don’t think Sir Keir or No 10 is overly stressing about when he gets out there.

A Downing Street insider insisted: ‘I don’t think Sir Keir, pictured, or No 10 is overly stressing about when he gets out there.

‘But he does want to go and I think there’s a hunger to make that happen. They [Sir Keir and Mr Trump] have had dinner together, and the PM does speak to him quite a bit’.

The insider hinted that the Government was ready to give Mr Trump his desired state visit, which would potentially make him the first elected politician in modern history to have been granted two such trips, hosted by the Royal Family. The late Queen entertained Mr Trump during a three-day visit in 2019.

Despite Sir Keir’s remarks to the FT, the Trump ally said: ‘A trade deal with the UK isn’t top of Trump’s agenda. You guys [in the UK] need it more than we do.

‘Having said all that Trump does have a “sentimental love” for the UK – for family reasons mostly [his mother was Scottish]. He’s bringing Churchill’s bust back into the Oval Office on day one. But he’s pragmatic and this time around it’s all business. What can you do for us? The onus is on the UK to make an attractive trade offer.

‘Yes, there will always be a special relationship but that’s increasingly in the rear view mirror.’

Meanwhile, Navin Ramgoolam, the prime minister of Mauritius, has accused the UK Government of trying to fast-track its deal to surrender the Chagos Islands, then backing out as Trump’s inauguration loomed following pressure from the incoming President.