Republican congressman Justin Amash, a frequent critic of Donald Trump who has called for the president’s impeachment, has announced he is leaving the party.

“Today, I am declaring my independence and leaving the Republican Party,” Mr Amash wrote in The Washington Post.

“No matter your circumstance, I’m asking you to join me in rejecting the partisan loyalties and rhetoric that divide and dehumanise us.

“I’m asking you to believe that we can do better than this two-party system – and to work toward it.

“If we continue to take America for granted, we will lose it.”

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While Mr Amash did not mention Mr Trump by name, he was the first Republican congressman to call for the president to be impeached.

Responding to Mr Amash’s announcement, Mr Trump tweeted: “Great news for the Republican Party as one of the dumbest and most disloyal men in Congress is ‘quitting’ the Party.

“No Collusion, No Obstruction! Knew he couldn’t get the nomination to run again in the Great State of Michigan. Already being challenged for his seat. A total loser!”

In May, Mr Amash clashed with right-wing voters in his constituency after he said they would be “appalled at much of [Mr Trump’s] conduct” outlined in volume II of special counsel Robert Mueller’s report into Russian interference in the US election.

“I was appalled by it,” he said at a town hall meeting at Grand Rapids in his home state of Michigan. ”And we can’t let conduct like that go unchecked.”

He has also claimed he would not rule out challenging Mr Trump as a third party candidate in the 2020 election.

Mr Trump has previously called Mr Amash ”a total lightweight who opposes me and some of our great Republican ideas and policies” and ”a loser who sadly plays right into our opponents hands!”

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Mr Amash, the son of Palestinian and Syrian immigrants, has previously been denounced by the Republican Party following his calls for impeachment.