Joe Biden knew he could beat Hillary Clinton in the race for the Democratic presidential nomination but decided not to run because he feared a “stop at nothing” smear campaign by her supporters, he reveals in a new memoir.

The man who served as Barack Obama’s vice-president remains a favourite among party faithful, many of whom believe he would have fared better in the states that delivered the White House to Donald Trump.

His words are certain to deepen splits among Democrats following their defeat and reignite speculation the 74-year-old is preparing for one last run.

In Promise Me Dad: A Year of Hope, Hardship and Purpose, due to be published next week, Mr Biden discusses his decision not to stand in the wake of his son Beau’s death.

He describes meeting Mrs Clinton in February 2015 when she was preparing her campaign and probing his plans.