London Mayor Sadiq Khan, in a Tuesday opinion piece for The Guardian, called out President Trump for boosting “divisive, far-right politics” worldwide in recent years.

“We must unite to take on the reactionary populists and nativists who are exploiting economic concerns, the atomisation of modern life and a growing distrust of political and media institutions – something we have seen in countries across Europe and, of course, in the US,” Khan said in his Guardian piece.

“President Donald Trump and his coterie have perhaps done the most to fan the flames of divisive, far-right politics around the world in recent years,” he added. “When he came to the UK on his first state visit, I highlighted how the president had deliberately used xenophobia, racism and ‘otherness’ as an electoral tactic.”

Trump arrived England on Tuesday evening for a state visit, where he is expected to meet King Charles III and other members of the royal family at Windsor Castle, about 25 miles west of London. During his trip abroad, the president is also scheduled to meet British Prime Minister Keir Starmer, and the two will likely discuss tariffs, the war in Ukraine and the conflict in Gaza.

In his piece, Khan asked his country’s leaders to “ensure our special relationship includes being open and honest with each other.”

“At times, this means being a critical friend and speaking truth to power – and being clear that we reject the politics of fear and division,” Khan said, later adding, “Those who seek to divide us will find a city determined to defend its liberal, democratic values more fiercely than ever.”

Trump has gone after Khan before, describing him as a “stone cold loser” on social media in 2019.

“.@SadiqKhan, who by all accounts has done a terrible job as Mayor of London, has been foolishly ‘nasty’ to the visiting President of the United States, by far the most important ally of the United Kingdom,” Trump said on the social platform X at the time.

“He is a stone cold loser who should focus on crime in London, not me,” he added.

Last year, Khan said world leaders were closely monitoring the U.S. presidential election between Trump and former Vice President Kamala Harris, stressing the worldwide implications of its results.

“What I’d say in a respectful way to Americans is: I don’t think you realize that the rest of the world is watching because we’ve got skin in the game,” Khan said last year in an interview with Politico.

The Hill has reached out to the White House for comment.