It's not the first time the journalist in question has asked politicians about their weight.

In a 2014 interview with Chancellor George Osborne, Walters wrote: "It is impossible not to notice his dramatic weight loss. He is a real skinny malink. 'Am I?' he says, modestly patting his slim line waist."

Osborne responded that he had "lost a couple of stone" on the 5-2 diet.

Kendall is up against Andy Burnham, Jeremy Corbyn and Yvette Cooper in the Labour leadership contest.

The party's previous leader Ed Miliband stepped down after the party suffered catastrophic losses in the General Election in May.

A vote will take place next month, with the new leader announced on 12 September.

In the Mail interview this weekend, Kendall also hit out at implications among some Labour commentators that she is unfit to be a leader because she is single, and doesn't have children.

"When people say, 'You don’t have a family' it makes my blood boil. I thought, 'Yes I do, I have my dad, my mum, my brothers and nieces,'" she said.

"...As you get older, of course you want to be settled, but life changes and it doesn’t work out. Who knows what will happen? That’s all I say. I am a person who loves and wants to be loved."

Slamming down sexism; Labour candidate Liz Kendall hits out at 'unbelievable' question about her weight