Washington DC - A leading law firm sanctioned by US President Donald Trump for its work with Democrat Hillary Clinton's 2016 presidential campaign filed suit against his administration on Tuesday.

Trump, in an executive order last week, suspended the security clearances of employees of Perkins Coie LLP and barred them from accessing federal government buildings.

Trump also asked government agencies to terminate contracts with Perkins Coie and refrain from hiring any of its employees.

Perkins Coie, in a complaint filed in a federal court in Washington, called Trump's executive order "an affront to the Constitution" and an attempt to "bully" those with adverse views.

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"The Order imposes these punishments as retaliation for the firm's association with, and representation of, clients that the President perceives as his political opponents," it said.

Perkins Coie said it was being targeted because the president views it "as aligned with the Democratic Party by reason of its representation of the 2016 Clinton presidential campaign" and its successful handling of legal challenges to Trump's false claims that he won the 2020 election.

"Perkins Coie's ability to represent the interests of its clients – and its ability to operate as a legal-services business at all – are under direct and imminent threat," it said.

Perkins Coie was founded in Seattle, Washington, more than 100 years ago and currently has some 2,500 employees, about half of whom are attorneys.

The Republican president also retaliated last month against another law firm, Covington & Burling, which did pro bono work for Jack Smith, the former special counsel who brought two federal criminal cases against Trump after he left the White House in 2021.

Both cases were dropped after Trump won November's presidential election.