The US president-elect's lawsuit comes days after the defamation settlement was reached with ABC News.

United States President-elect Donald Trump has filed a lawsuit accusing a newspaper and a polling firm of engaging in "blue election interference" by publishing a pre-election survey that underestimate its popularity.

The lawsuit, filed late Monday, accuses The Des Moines Register newspaper, its parent company Gannett and pollster Ann Selzer of intentionally downplaying Trump's support in a poll that showed him trailing Democratic presidential candidate Kamala Harris.

The Nov. 2 poll, which showed Harris leading by three percentage points in Iowa, drew widespread attention as Trump easily carried the Midwest state in the 2016 and 2020 elections.

Trump won Iowa by more than 13 percentage points in last month's presidential election.

"Selzer's 'missing' the vote was not an astonishing coincidence — it was intentional," the lawsuit filed in Iowa's Polk County said. "As President Trump remarked, 'She knew exactly what she was doing.'"

The lawsuit, which bases its claims on alleged violations of Iowa's consumer fraud statute, seeks treble damages as determined by a jury.

Lark-Marie Anton, a spokeswoman for The Des Moines Register, said the newspaper stands by its reporting and considers the lawsuit to be without merit.

"We acknowledged that the Selzer/Des Moines Register primary poll did not reflect the ultimate margin of President Trump's Election Day victory in Iowa through the poll's full demographics, crosstabs, weighted and unweighted data, as well as a technical explanation from pollster Ann Selzer,” said Anton.

Selzer did not immediately respond to a request for comment, but said in an interview with PBS last week that she was confused as to why anyone would think she engineered the poll to generate a specific result.

Trump's lawsuit comes just days after ABC News agreed to settle a defamation suit he brought over anchor George Stephanopoulos's inaccurate claim that he had been found civilly liable for rape.

The Foundation for Individual Rights and Expression, a civil liberties organization, condemned the lawsuit as a "direct attack" on the First Amendment to the US Constitution, which guarantees the right to free speech.

“When newspapers and polling firms are sued for 'deceptive practices' for publishing stories and poll results that politicians don't like, every media outlet's First Amendment rights are threatened. Getting a poll wrong is not election interference or fraud,” the group said.

Trump, who is sued CBS News over an interview with Harris that he claims was fraudulently redacted, faces steep legal hurdles in his lawsuits because of the US's speech protections, which are among the strongest in the world.

Still, the lawsuits could create problems for news organizations by exposing potentially embarrassing internal communications and subjecting journalists and executives to depositions.