Falsehoods spread by President Donald Trump's White House could put "lives at risk" according to a senior congressman.

Democrat Adam Schiff, of California, was speaking during the fallout from a number of false claims made by Mr Trump and his staff regarding the size of the crowd at his inauguration ceremony.

Press secretary Sean Spicer made the demonstrably false claim that the crowd was the biggest ever, "period", while the President himself claimed between one and 1.5 million people had attended, which photographs disproved.

Mr Schiff, a member of the House Intelligence Committee, told Politico: "It absolutely puts lives at risk. If the president claims that Iran is cheating on the nuclear accord, or that North Korea is about to test a nuclear device on an intercontinental missile, the public needs to believe him, and if he so undermines his credibility we can’t build an international coalition … it has the gravest consequences."

Mr Trump's adviser Kellyanne Conway told an incredulous NBC anchor on Sunday that Mr Spicer was dealing in "alternative facts", not falsehoods.