Democrat Doug Jones has been certified the winner of the state’s US Senate race despite a legal challenge by Republican Roy Moore, whose campaign was derailed by accusations of sexual misconduct with teenage girls.

Mr Jones won the seat, vacated when President Donald Trump appointed Jeff Sessions as attorney general, by about 20,000 votes, or 1.5 percentage points, election officials said.

That made him the first Democrat in a quarter of a century to win a Senate seat in the state.

Alabama Secretary of State John Merrill met with other members of the state canvassing board, Governor Kay Ivey and Attorney General Steve Marshall, to certify the result.

Mr Moore’s challenge alleged there had been potential voter fraud in the December 12 election that denied him a chance of victory.

Roy Moore refused to concede the vote. Photo: Getty

His filing on Wednesday in the Montgomery Circuit Court sought to halt the meeting scheduled to ratify Mr Jones’ win on Thursday.

Mr Moore declined to concede defeat despite being urged by Mr Trump to do so.

Janet Porter, a spokeswoman for Mr Moore’s campaign, said in an interview with CNN that the challenge aimed to ensure that votes were properly counted.

“It’s incumbent on the Alabama secretary of state to make sure,” she said.

Regarding the claim of voter fraud, Mr Merrill said more than 100 cases had been reported.

“We’ve adjudicated more than 60 of those. We will continue to do that,” he said.

A day after the election, Mr Merrill had told CNN it was “highly unlikely” that Mr Jones, 63, would not be certified as the winner.

Seating Mr Jones will narrow the Republican majority in the Senate to 51 of 100 seats.