A Republican politician has reportedly quit the party because of Donald Trump's “erratic and misguided leadership”.

Ken Rizer, a retired Air Force Pilot, took Facebook to announce his decision after the US leader met with Vladimir Putin in Helsinki and suggested that he did not believe that Russia had meddled in the 2016 presidential election.

Facing a backlash at home, the president later suggested he misspoke had meant to say it "wouldn't" be Russia.

But not before Mr Rizer had announced he was leaving the party, according to the Des Moines Register.

“(Former national security adviser) HR McMaster wrote a fabulous book called Dereliction of Duty, which outlined how the joint chiefs failed to step up and oppose President (Lyndon) Johnson’s disastrous Vietnam War policy,” he said in a post that has since apparently been made inaccessible to the public.

Ken Rizer (Iowa legislature)

"Military officers read and studied this book, presumably so that we wouldn’t repeat similar mistakes. We’re at another such moment in our foreign affairs where people of character in this administration need to speak up or resign.

"As for me, I can no longer call myself a Republican given the erratic and misguided leadership of the president. I will always be a (Ronald) Reagan conservative, but find no place for such views in Trump’s world. Until the Republican Party recovers its values, my party affiliation will be ‘No party.’”