A Democratic congressman filed a lawsuit on Friday against former president Donald Trump, his son Donald Jr, his lawyer Rudy Giuliani and a Republican lawmaker for allegedly inciting the January 6 attack on the US Capitol.

Trump, 74, and the other defendants waged a "campaign of lies and incendiary rhetoric" which led to the assault on Congress, Representative Eric Swalwell of California charged in the civil suit filed in a US District Court in Washington.

Another Democratic congressman, Representative Bennie Thompson of Mississippi, filed a similar suit against Trump last month.

Both suits cite a little used law, the Ku Klux Klan Act, to make the case against the former president.

The 1871 rule was designed to prevent the white supremacist KKK from intimidating elected officials.

Trump, Donald Jr, Giuliani and Representative Mo Brooks, a congressman from Alabama, all spoke at a rally which preceded the January 6 attack on Congress by Trump supporters seeking to block the certification of Democrat Joe Biden's election victory.

"Unable to accept defeat, Donald Trump waged an all out war on a peaceful transition of power," Swalwell said in a statement announcing the lawsuit.

"He lied to his followers again and again claiming the election was stolen," he said, "and finally called upon his supporters to descend on Washington DC to 'stop the steal.'"

"The defendants assembled, inflamed and incited the mob, and as such are wholly responsible for the injury and destruction that followed," Swalwell said.

The suit demanded unspecified monetary and punitive damages to be determined at a jury trial.

Swalwell was one of the impeachment managers for Trump's trial in the Senate on the charge of inciting insurrection.

Trump was impeached by the Democratic-majority House of Representatives for his role in inciting the attack on the Capitol but acquitted by the Senate.

Thompson and the NAACP, a civil rights organization, filed suit against Trump, Giuliani and two right-wing groups, the Proud Boys and Oath Keepers, last month.

Jason Miller, a Trump spokesman, responded to the latest lawsuit in a statement to The Washington Post. "Eric Swalwell is a low-life with no credibility," Miller said.