Sadiq Khan has said "far-right" leaders looked up to Donald Trump, a day after he was dubbed a “loser” by the US president.
The London mayor said leaders he found "abhorrent" all looked up to Mr Trump, branding him their "poster boy".
"It should be a source of concern to us that Donald Trump is the poster boy for the far-right movement around the world," Mr Khan said.
“There are many leaders whose views I find abhorrent - in Hungary, in Italy, in France, here in the UK, and the poster boy they look up to is Donald Trump.”
Mr Khan accused the US leader of “playground” behaviour after he tweeted that the London mayor was a “stone cold loser” yesterday.
“Some of the things that he has done as president are deeply objectionable, far more objectionable than silly tweets he might send,” he said.
"This is not about childish behaviour, this is about us as a city and many people around the country making clear our views about some of the things said and done by Donald Trump."
Mr Khan has urged Prime Minister Theresa May to challenge Mr Trump on his more controversial behaviour during the three-day state visit.
"These are big issues and I'm hoping that Theresa May stands up for our country and does say boo to a goose.”
He’s insisted he is “very pro-America”, but stood behind Labour leader Jeremy Corbyn’s decision to boycott a dinner for Mr Trump hosted by the Queen.
"What shouldn't happen is a state banquet and a state visit with the red carpet rolled out. I think it's inappropriate.”
“I think it sends the wrong message to be seen to condone some of the things this president has said and done."