A voting machine manufacturer sued Rudy Giuliani, the lawyer for former US president Donald Trump, on Monday after he claimed the company had cost Trump last November's election.

In a defamation lawsuit seeking damages of $1.3 billion, Dominion Voting Systems said Giuliani and other Trump allies had damaged its reputation by alleging its widely used voting machines were part of a "massive fraud" that Giuliani claimed had "fixed the vote" for now-President Joe Biden.

Dozens of state and federal rulings, as well as the US Congress, have rejected such claims.

But the allegations underpinned what Dominion called the "Big Lie" behind the January 6 attack on the US Congress by Trump supporters attempting to overturn Biden's victory.

Former New York mayor Giuliani and his allies "manufactured and disseminated the 'Big Lie,' which foreseeably went viral and deceived millions of people into believing that Dominion had stolen their votes and fixed the election," Dominion said in the suit, filed in Washington federal court.

Giuliani did not immediately comment on the lawsuit.

Dominion said Giuliani, 76, had requested $20,000 a day from Trump's campaign for pushing the fraud argument, which he also used to publicize other commercial ventures -- selling gold coins, cigars and cyber security services.

"Even after the United States Capitol had been stormed by rioters who had been deceived by Giuliani and his allies, Giuliani shirked responsibility for the consequences of his words and repeated the Big Lie again," it said in the suit.

Dominion said Giuliani knew the claims that Dominion's voting machines produced false counts were bogus because, while he repeatedly promoted the idea in public, he declined to say so in court before a judge.

"He was unwilling to make false election fraud claims about Dominion and its voting machines in a court of law because he knew those allegations are false," it said.

The viral claims saw Dominion pilloried online and in conservative media and forced the company to repeatedly defend its reputation, despite no evidence that its vote tallies were erroneous.

It was the second such case filed by Dominion.

On January 8 it sued Sidney Powell, another attorney representing Trump in the effort to overturn the election results, also for $1.3 billion.

Similar to the Powell suit, the Giuliani suit said he worked "in concert with" conservative media companies Fox News, Fox Business, Newsmax, One America News Network, and The Epoch Times to push "defamatory falsehoods."

It was not clear if Dominion intended action against any of those companies or against Trump himself, who also questioned Dominion's technology.

pmh/wat