London mayor Sadiq Khan has joined more than 30 British politicians to publicly support the four American congresswomen who were racially attacked by Donald Trump earlier this week.

Khan, a long-standing and vocal critic of the US president, signed an open letter addressed to Alexandria Ocasio-Cortez, Ilhan Omar, Rashida Tlaib, and Ayanna Pressley, expressing “disgust” at Trump’s racist tweets in which he suggested that the women “go back and help fix the totally broken and crime infested places from which they came”.

Omar, a Somali refugee who is one of the first two Muslim women ever to serve in Congress, became a US citizen as a teenager. The other three women were all born in the US.

Khan, alongside MPs including Labour leader Jeremy Corbyn, responded to British anti-racism group Hope Not Hate’s call to share a message of solidarity with the first-term Democrats.

"We are disgusted by Donald Trump's attack on you. His blatant, unashamed racism has appalled people around the world,” reads the letter.

"You embody the best of America. Its diversity is its strength. Thank you for showing the world that America can still provide leadership to be proud of, even when the White House has abdicated that role. We stand in solidarity with you."

The letter is also signed by 13,809 of the campaign group’s activists.