One of Donald Trump's senior advisers used a Sunday television appearance to repeat an unfounded claim that "thousands" of people were driven to the state of New Hampshire to vote illegally in November's election.

The voter fraud allegation was first made by the President himself in a meeting with senators. Federal Electoral Commissioner Ellen Weintraub called it an "astonishing" claim that "cannot be ignored", and urged Mr Trump to provide evidence.

Senior adviser Stephen Miller did the rounds of Sunday politics programmes in the US and was praised by Mr Trump for his performance. During one, he asserted the New Hampshire claim and other fraud claims a number of times without giving evidence for them.

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On ABC, he told presenter George Stephanopoulos: "I can tell you that this issue, of busing voters into New Hampshire, is widely known by anyone who's worked in New Hampshire politics, it's very real, it's very serious.

"This morning, on this show, is not the venue for me to lay out all the evidence, but I can tell you this: voter fraud is a serious problem in this country.

"You have millions of people who are registered in two states, or who are dead who are registered to vote, and you have 14 per cent of non-citizens, according to academic research, at a minimum, are registered to vote."

Pressed by Mr Stephanopoulos on the basis for his claim, he said: "Go to New Hampshire, talk to anyone who's worked in politics there for a long time. Everybody's aware of the problem in New Hampshire."

Challenging Mr Miller a second time, Mr Stephanopoulos said: "I'm asking you as the White House senior policy adviser, the President made a statement saying he was the victim of voter fraud. Do you have any evidence?"

Mr Miller replied: "If this is an issue that interests you, then we can talk about it more in the future."

Mr Stephanopoulos said: "You have provided absolutely no evidence." Mr Miller, repeatedly glancing out of shot, said: "The White House has provided enormous evidence." He added there were "massive numbers" of non-citizens registered to vote.

"That's the story we should be talking about, and I'm prepared to go on any show, anywhere, any time and repeat it and say the President of the United States is correct 100 per cent."

President Trump later tweeted: "Congratulations Stephen Miller- on representing me this morning on the various Sunday morning shows. Great job!"

Commissioner Weintraub, appointed by George W Bush in 2002, said: "President Trump has alleged an astonishing voter-fraud scheme that he claims denied him and former Senator Kelly Ayotte victory in the state of New Hampshire in the 2016 elections."

"As a commissioner on the Federal Election Commission, I am acutely aware that our democracy rests on the faith of the American people in the integrity of their elections."