Rishi Sunak has sparked a row after lining up Sir Tim Barrow, his national security adviser, as Britain's next ambassador to the US.

The Prime Minister is said to have plumped for Sir Tim, who played a key role in the Brexit negotiations with the EU, for the prestigious position.

He is expected to take over from Dame Karen Pierce, the current ambassador, after the US election in November.

But Mr Sunak prompted anger from Labour who questioned why the PM was 'rushing through' a key diplomatic appointment before the UK's own general election.

They warned they could 'revisit' Sir Tim's appointment if Sir Keir Starmer replaces Mr Sunak in Downing Street.

Mr Sunak's decision to send Sir Tim to Washington DC is also a blow to those who had been touting Nigel Farage, an ally of Donald Trump, for the ambassadorship.

Rishi Sunak has sparked a row after lining up Sir Tim Barrow, his national security adviser, as Britain's next ambassador to the US

Prior to becoming national security adviser, Sir Tim served as the UK's ambassador to the EU, which saw him tasked with formally triggering Article 50 in March 2017

Labour warned they could 'revisit' Sir Tim's appointment if Sir Keir Starmer replaces Mr Sunak in Downing Street

Mr Sunak's decision to send Sir Tim to Washington DC is also a blow to those who had been touting Nigel Farage, an ally of Donald Trump, for the ambassadorship

The PM all but confirmed Sir Tim's appointment as Britain's new ambassador to the US when he said he will appoint General Gwyn Jenkins (left) as his new national security adviser

The PM all but confirmed Sir Tim's appointment as Britain's new ambassador to the US when he today said he will appoint a top general as his new national security adviser.

Mr Sunak said General Gwyn Jenkins, one of the most senior officers in the Armed Forces, has the 'requisite set of skills' for the role.

Prior to becoming national security adviser, Sir Tim served as Britain's ambassador to Russia and then the UK's top diplomat in Brussels.

This saw him tasked with formally triggering Article 50 of the EU treaty to pave the way for the UK's exit from the bloc.

He was subsequently a prominent member of Britain's negotiating team in Brussels during the Brexit process.

Sir Tim's likely appointment as the UK's man in Washington DC, first reported by the Financial Times, has sparked anger among Labour ranks.

A party official told the newspaper: 'By needlessly rushing through vital diplomatic appointments so close to both the UK and US elections, the Tories are putting their party interests before the national interest once again.

Labour also warned they could override Mr Sunak's decisioon and install their own preferred candidate in the role if Sir Keir becomes PM.

The official added: 'If Labour wins the privilege of forming the next government, we would of course reserve the right to revisit senior diplomatic appointments made in the run-up to the general election.'

Mr Farage told The Telegraph that Sir Tim was 'not exactly an imaginative choice from a dying Government'.

He added: 'He is a better appointment than some, but can he connect with a Trump White House?'

As a strong ally of ex-US president Mr Trump, who is seeking a return to the White House as the Republican nominee at November's election, Mr Farage had been touted by some as a possible UK ambassador to Washington DC.

Fretting Tory MPs recently urged Mr Sunak to name Mr Farage as Britain's next top diplomat in America as part of a deal to stop him spearheading Reform UK's general election campaign.

Conservatives are increasingly worried about Reform's rise in opinion polls and fear a return by Mr Farage to frontline politics could turbocharge the insurgent party's growing popularity.

Both Mr Farage and Reform rejected the idea of any pact between him and the Tories ahead of the general election.

Asked about the looming change of ambassador to Washington DC, Mr Sunak today told reporters travelling with him to Poland: 'The ambassadorial or diplomatic appointments are always made in the usual way, which they will be.

'And it's entirely normal for those to be made in advance, entirely normal, entirely keeping with precedent because ambassadors designate often go and acclimatise themselves and build relationships before they formally start.'

Announcing Gen Jenkins' appointment, Mr Sunak said: 'I'm really pleased that Gwyn is going to do this job.

'In an incredibly uncertain and increasingly dangerous world, it's important the person doing this job has the requisite set of skills to provide advice to me and to help navigate that landscape.

'As many of you know, he has a very distinguished career in the Armed Forces, he was in the special forces as well as serving in No10 as a military advisor and deputy national security adviser.

'I'd just point out it's the first time we've had someone with a military background in that job and obviously he has worked in No10 as well so has that policy experience.

'We need someone in that job who can blend a range of different skills together, diplomatic, intelligence, military operations.

'I have worked with Gwyn very closely since I've been PM – he's first-rate, the country is lucky to have his service, the Government is very lucky to have his advice.'

The PM also said he was 'very grateful' to Sir Tim.

'He's been at the heart of foreign policy with me and really strengthening the UK's alliances and making sure we are involved and engaged and influential on the world stage,' Mr Sunak said.

Gen Jenkins is currently the vice chief of the defence staff.