London mayor Sadiq Khan blasted president Donald Trump and Europe's right-wing leaders -- Viktor Orbán in Hungary, Matteo Salvini in Italy, Marine Le Pen in France and Nigel Farage in the UK -- as torchbearers of the division who use "new sinister methods to deliver their message."

The outspoken mayor, who has long been a foe of Trump, delivered a scathing indictment of the American businessman on the eve of his three-day state visit to the United Kingdom. Trump and his party arrived on Monday morning but not before Trump attacked Khan as being a "stone cold loser" in another nasty tweet.

Khan's spokesman replied to Trump's insulting tweet, saying "childish insults" should be beneath the US president.

"Sadiq is representing the progressive values of London and our country, warning that Donald Trump is the most egregious example of a growing far-right threat around the globe."

In an editorial titled, "It's un-British to roll out the red carpet for Donald Trump," published by The Guardian, Khan compared Trump to the fascists who destroyed Europe before and during World War II.

"In years to come, I suspect this state visit will be one we look back on with profound regret and acknowledge that we were on the wrong side of history," wrote Khan.

Khan enumerated but a few examples of Trump's racism and fascism. He pointed to Trump's remarks after the August 2017 attack by neo-Nazis and right-wing racists in Charlottesville, Virginia; his administration's family separation immigration policy, and his support for former British foreign secretary Boris Johnson for prime minister "because he believes it would enable him to gain an ally in Number 10 for his divisive agenda."

"Donald Trump is just one of the most egregious examples of a growing global threat," wrote Khan.

Khan further said Trump is part of the global rise of "far right" hate mongers that threaten "our hard-won rights and freedoms and the values that have defined our liberal, democratic societies for more than seventy years."

Included in Khan's hall of shame are Orbán, Salvini, Le Pen in France and Farage.

Trump has never been popular in the UK and protests against his visits will take place in London, Manchester, Belfast, and Birmingham, among many others.