Yvette Cooper has suggested that the Labour leadership campaign is in danger of dragging politics back to the 1950s and blasted sexism from Andy Burnham's supporters.
The shadow home secretary said the message coming out of Burnham's camp was that she and Liz Kendall should drop out of the race and "leave it to the boys".
Speaking in an interview with the Guardian, Cooper said: "We can't go back to an old fashioned Labour party – not just back to the politics of the 80s but of the politics of the 50s – treating women as incapable of the top jobs, and a party led by two men.
Yvette Cooper has blasted sexism from Andy Burnham's supporters
"It's been a startlingly retro campaign debate. Andy's campaign seem to be calling for Liz and I to bow out and leave it to the boys, or suggesting that somehow women aren't strong enough to do the top jobs.
"Liz has been asked about her weight, I've been asked (on [BBC Radio 4's] Woman's Hour of all places) about whether I can possibly do this job because of my husband, and any talk about me being a working mum has been used as a sexist way to divide Liz and I, and criticise Liz for not having children."
A major row broke out this week over a Times piece written by shadow justice secretary Lord Falconer, headlined "Women are not tough enough to lead Labour".
In the article, the Burnham supporter said "neither Yvette or Liz were able to steer the party through the challenging years ahead".
However, Lord Falconer insisted he was horrified by the headline and had never implied their gender was an issue.
Cooper said she was determined to put equality at the centre of her bid for the leadership.
"I believe that the campaign for equality has stalled. Disability hate crime is growing, maternity discrimination has increased, homophobic bullying isn't being challenged, antisemitism and islamophobia have increased," she said.
"Meanwhile the new emerging high tech jobs of the digital age are being predominantly done by men, and there is still a longstanding problem of lack of black and ethnic minority police."
Lord Falconer's article sparked a row earlier this week
Cooper also revealed for the first time how she cried on election night as her husband Ed Balls lost his seat.
"One of the toughest things was talking on the phone to the children – our oldest had her first GCSE that day – trying to stop them getting upset as they watched the headlines come through.
"But the thing about Ed is that he is so strong and also so generous. He gave a beautiful speech that had not just me but I think half the Labour party across the country in tears as we watched."