Washington (AFP) – The White House on Tuesday confirmed that President Donald Trump believes millions of people voted illegally in the November election, but declined to provide evidence to support that claim.

Hours after Trump told congressional leaders that as many as five million people could have voted illegally, White House spokesman Sean Spicer confirmed the president’s belief.

“The comment he said was three to five million people could have voted illegally based on the studies he’s seen,” said Spicer.

“I think the president has believed that for a while based on studies and information he has.”

There is no public evidence of widespread illegal voting in last year’s poll.

If proven, it would be one of the biggest political scandals in US history and could fundamentally undermine faith in US democracy.

Spicer said the Republican president nonetheless had confidence in the election outcome.

Trump lost the popular vote to Democrat Hillary Clinton by around 2.9 million votes, but he won the all-important state-weighted electoral college.

Spicer suggested that the “studies and evidence” that “people” have brought to Trump included a study that suggested 14 percent of people who voted “were non-citizens.”

Trump has previously cited a Pew report from 2012 that concluded more than “1.8 million deceased individuals are listed as voters.”

That report did not provide evidence that dead people voted, or that others voted in their name.

Trump has also cited an Old Dominion University study which suggested 14 percent of non-citizens said they were registered to vote.

That study has been dismissed as having flawed methodology, with a sample size of under 1,000 and no link between being registered to vote and actually voting.

Asked whether the White House could open an investigation into such vast fraud, Spicer said “maybe we will.”

But when asked again he said “Anything is possible.”

“There is no investigation. I said it was possible. Anything is possible. It was a hypothetical question.”

Spicer refused to say what impact such fraud could have on democracy.