Liz Kendall told a Mail on Sunday journalist to "f*** off" when she was asked how much she weighed during an interview.
The Labour leadership contender said the question was "unbelievable" as she questioned whether a male politician would be asked about their weight.
The Leicester West MP said she "cannot wait for a world when women are judged the same as men".
In the much-criticised article, journalist Simon Walters : "In fact she looks the same weight as the Duchess – about 8st – though when I ask she slaps me down with a raucous ‘f*** off!’, adding quickly: ‘Don’t print that.’"
The article also says that Ms Kendall maintains her "lithe figure" by jogging 20 miles a week.
I just think it's unbelievable that in the 21st Century women still get asked such very, very different questions from men.
Ms Kendall is up against Andy Burnham, Yvette Cooper and Jeremy Corbyn in the race to succeed Ed Miliband.
Social media users were equally as critical of the article, accusing the Mail of sexism.
She is not the first MP to hit out at the media's treatment of female politicians.