The White House will not rule out pardoning Hillary Clinton for any offences she may have committed over her use of a private email server, after Donald Trump's warning that she would be jailed if he became president.

A spokesman for President Barack Obama left open the possibility of a pardon, which would shield Mrs Clinton from prosecution even after the President leaves office.

"We don't talk about the President's thinking, particularly with respect to any specific cases that might apply to pardons or commutations," Josh Earnest said.

Rudy Giuliani, the former New York mayor and a front-runner to be Mr Trump's attorney general, said yesterday that Mr Obama should allow any investigation into Mrs Clinton, or the foundation run by former president Bill Clinton, to run its course.