UK politicians are among the signatories of a message of solidarity with Democratic Reps. Ilhan Omar, Alexandria Ocasio-Cortez, Rashida Tlaib, and Ayanna Pressley after President Donald Trump suggested they should "go back" where they came from.

The Labour Party leader, Jeremy Corbyn, and Mayor Sadiq Khan of London were among more than 13,000 signatories of an open letter created by a UK anti-racism group.

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

The letter came after supporters at a Trump rally Wednesday night chanted "send her back" in reference to Omar.

Dozens of British politicians, including the Labour Party's leader, Jeremy Corbyn, and Mayor Sadiq Khan of London, are among those to sign an open letter expressing solidarity with Rep. Ilhan Omar and the three other US congresswomen targeted by President Donald Trump in recent days.

The letter, created by a UK anti-racism group, expressed solidarity with Reps. Alexandria Ocasio-Cortez, Omar, Rashida Tlaib, and Ayanna Pressley, who Trump on Sunday suggested should "go back" to the "crime infested" countries they came from even though all four are US citizens and three were born in the US.

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

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"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."

In a separate message shared on Facebook, Khan wrote that "love and solidarity will always trump hate," adding that the four congresswomen "represent hope for the future." He concluded: "Their home is America, but their message crosses borders."

The message of support followed a campaign rally Wednesday in which supporters at a Trump rally joined in chanting of "send her back," in reference to Omar.

Watch Trump supporters chant 'send her back'

The letter was compiled by the anti-racism group Hope Not Hate and signed by 13,809 of its supporters.

Its campaign director, Matthew McGregor, said Trump had given succor to racists around the world.

"Donald Trump's racist tweets were a disgusting attack on four congresswomen of color," he said. "Trump's racism crosses borders — his slurs have an impact around the world and have given heart to white nationalists everywhere.

"We want Alexandra Ocasio-Cortez, Ilhan Omar, Rashida Tlaib, and Ayanna Pressley to know that from across the political spectrum in Britain, thousands and thousands of people are grateful for their leadership, for the hope they give people, and that they have our solidarity."

The letter was signed by opposition politicians from the Labour Party, Green Party, and Plaid Cymru.

Here is who signed the letter