President Donald Trump threatens his former chief strategist Steve Bannon with legal action over “defamatory” statements about Trump's son and son-in-law over a meeting with Russians during the 2016 US presidential campaign.

President Donald Trump on Wednesday blasted former White House chief strategist Steve Bannon as having “lost his mind” in the fallout over damaging comments Bannon made about Trump’s son Donald Trump Jr in excerpts from a new book.

When Steve Bannon gave a free-wheeling interview to a small left-wing magazine this week, he spoke as if he -- the White House's 'great manipulator' -- was back on top.