London, UK - British Prime Minister Keir Starmer on Friday confirmed the appointment of veteran Labour politician Peter Mandelson, a former minister and EU trade commissioner, as the next ambassador to the US.

Mandelson (71) will take up the post "early next year," Downing Street said, just as president-elect Donald Trump returns to the White House for a second term.

"The United States is one of our most important allies and as we move into a new chapter in our friendship, Peter will bring unrivalled experience to the role and take our partnership from strength to strength," Starmer said in a statement.

Mandelson's appointment comes amid reported unease within the UK government about the prospects for London's so-called "special relationship" with Washington during Trump's second presidency.

United Kingdom (UK) Northern Ireland's Game Of Thrones trees in danger as preservationists demand action

The US president-elect's threat to impose blanket tariffs on all imports is a particular concern for Starmer's new Labour government, which has vowed to boost Britain's economic growth rates.

The UK leader has been criticized heavily this year by billionaire Trump confidant Elon Musk.

Mandelson will replace Karen Pierce, the current ambassador in Washington, who has been credited with forging strong links with the many staffers and advisors in Trump's team.

But in a sign of the likely fraught nature of transatlantic ties under Trump, the choice drew an immediate rebuke from a senior figure within his presidential election team.

Campaign co-manager Chris LaCivita took to X to note Mandelson's previous description of the Republican leader as "little short of a white nationalist and racist."

"This UK govt is special – replace a professional universally respected Ambo with an absolute moron – he should stay home! SAD!" he posted.

United Kingdom (UK) UK woman marks 102nd birthday with "scary" skydive

The stinging criticism follows Trump's campaign team accusing Starmer's Labour party of interference during the recent US election over claims party staffers were helping his Democratic rival Kamala Harris.

Meanwhile, Mandelson's critique of Trump is reminiscent of disparaging remarks made by Foreign Secretary David Lammy, who previously called the incoming US president a "tyrant" and "xenophobic."

Lammy on Friday praised Mandelson's "wealth of experience in trade, economic and foreign policy from his years in government and the private sector."

"He will arrive in Washington DC as we deepen our enduring alliance with the incoming United States administration, particularly on growth and security," he added.

Mandelson, an EU trade commissioner from 2004 to 2008 who also co-founded the international public policy advisory firm Global Counsel, called his appointment "a great honour."

"We face challenges in Britain but also big opportunities," he said. "It will be a privilege to work with the government to land those opportunities, both for our economy and our nation's security, and to advance our historic alliance with the United States."

Mandelson is the first political appointment for the US envoy role in decades. Britain typically picks seasoned diplomats to be ambassadors.

In his statement, Starmer thanked Pierce "for her invaluable service for the last four years, and in particular the wisdom and steadfast support she has given me personally since July."

"She made history as the first woman to serve as UK ambassador to the US," he noted, adding that she had been "an outstanding representative of our country abroad."

Mandelson's return to a prominent government role represents a significant move for a politician who was last in the UK government when Gordon Brown was prime minister in the late 2000s.

He was a key architect in rebranding the Labour party in the 1990s after it had spent nearly two decades out of power.

A close ally of ex-prime minister Tony Blair, Mandelson headed several UK government departments between 1998 and 2001, but twice resigned after becoming embroiled in scandals. He reportedly had a close relationship and repeated meetings with serial sex trafficker Jeffrey Epstein.

Mandelson made a surprise 18-month return to government in 2008. More recently, he has served as a member of Britain's unelected House of Lords, the upper chamber of parliament.