The British ambassador to Washington, Dame Karen Pierce, is to be asked to stay in post as Donald Trump takes power, ahead of a complex shuffle of UK security and diplomatic jobs in the new year.

Pierce, with her deep knowledge of the Republican party, is considered to be the best person to help guide the Labour government during what could be a perilous transition from the Biden to Trump administrations.

The chancellor of the duchy of Lancaster, Pat McFadden, told Sky News on Thursday: “At the moment, she is doing an excellent job. She’s got the full confidence of the British government, and we want her to keep on doing the job that she’s doing. And I think she’s going to be a very important interlocutor and adviser for the UK government in this period of transition.”

He added: “I can’t say exactly when her term will end. She’s been doing it for a few years, but she’s there for the moment, she’ll be there for a while, and she’s doing an absolutely fantastic job for our country.”

Pierce posted to X on Wednesday after Trump was announced as the US election winner: “We look forward to deepening our already profound and successful partnership as we deal with the challenges of the 21st century.”

She was appointed as UK envoy to the UN in New York in 2018, and then in 2020 she was appointed ambassador to Washington.

There had been speculation that if Kamala Harris won, one of three Labour foreign policy specialists – Peter Mandelson, David Miliband or Valerie Amos – might be invited to take the post. But there is now likely to be a review of whether a Labour party figure would be the best person to have as interlocutor with the Trump team.

The Washington appointment is inextricably linked with the coming vacancies for the posts of permanent secretary at the Foreign Office and national security adviser, and potentially of UK ambassador to the UN.

Philip Barton has announced he is standing down as permanent secretary and it is possible Pierce could be offered that post, but Matthew Rycroft, the former permanent secretary at the Department for International Development and a previous UK ambassador to the UN, has also been mentioned.

The current envoy to the UN, Barbara Woodward, a former ambassador to China, is seen as a strong contender to be the new national security adviser post. The post of cabinet secretary is also becoming vacant.

Lord Mandelson is seeking to become chancellor of the University of Oxford, but has been told he could be ambassador at the same time.

The Foreign Office is hoping that a past outburst against Trump by the foreign secretary, David Lammy, which was highlighted by the Conservative leader, Kemi Badenoch, on Wednesday, will not affect the so-called special relationship.

But his team highlight the work he has done to connect with potential Republican foreign policy specialists, including a meeting with the vice-president-elect, JD Vance, in Munich this year and discussions with the former national security adviser Robert O’Brien. He has also spoken at the Hudson Institute thinktank where he highlighted his Christian roots.

The deeper risk for the UK is that it gets caught up in tariff war between the EU and the US. Jeremy Shapiro, a US-EU relations specialist at the European Council on Foreign Relations, said there was “a serious cultural divide between Labour and the Trump people”.

He predicted that “many European leaders will fall back on bilateralism and flattering, but I cannot say it will buy them anything”. He said the trade deficit between the US and the other country would be the issue most likely to animate Trump in any relationship.