Trump should admit Russians put him in the White House - Jimmy Carter

The oldest living former US President says Donald Trump would not be in the White House without Russian help.

Rumours the reality TV star and real estate magnate had help from the Kremlin have dogged Trump's presidency, and Jimmy Carter's claims won't help.

"I think a full investigation would show that Trump didn't actually win the election in 2016. He lost the election, and he was put into office because the Russians interfered on his behalf," 94-year-old Carter said at a panel on human rights on Friday, US media reported.

"The President himself should condemn it, admit that it happened, which I think 16 intelligence agencies have already agreed to say."

Asked by host Jon Meacham, a historian, if that made Trump's presidency illegitimate, Carter didn't deny it.

"Based on, what I just said, I can't retract."

Trump has repeatedly denied collusion with Russia to win the 2016 election. As Carter said, intelligence agencies have no doubt Russia made efforts to sow discord and swing the vote in Trump's favour over Hillary Clinton, but while a long-running investigation into the matter found numerous links between members of Trump campaign and Russia, collusion wasn't established.

Carter was US President from 1977 to 1981.