Joe Biden is fighting to keep his bid for the 2020 Democratic nomination on track as interest surges in Pete Buttigieg, the 37-year-old mayor of the rustbelt city of South Bend, Indiana.

Allegations of inappropriate behaviour towards women have dealt a serious blow to the 76-year-old former vice-president who, even though he has still formally to declare his candidacy, is seen as Donald Trump's likeliest opponent.

Mr Biden has apologised for his tactile approach, but he has found himself the butt of satire on Saturday Night Live.

His handling of the issue – including making a joke about the controversy on Friday - attracted further criticism over the weekend.

Colorado Senator Michael Bennet, who is considering entering the presidential race himself, condemned Mr Biden's flippant approach on State of the Union, a Sunday Morning political show.

"I don't think anyone should make jokes about it," he said.