Radical left-winger Jeremy Corbyn is on course to take Labour's top job after storming 20 points ahead of his rivals, according to private polling.
The backbencher is poised to top the ballot with 42%, with Yvette Cooper on 22.6%, Andy Burnham on 20% and Liz Kendall on 14%, according to the study seen by the Daily Mirror.
Mr Corbyn's lead narrows once second preferences have been taken into account, putting him just two points ahead on 51% while Ms Cooper comes in second on 49%.
It follows a public opinion poll last week that put the Islington North MP in line for a shock victory.
Earlier, Mr Corbyn described his embarrassment after women on an internet website branded him "very sexy" and "attractive in a world-weary old sea dog sort of way".
The bearded 66-year-old's blushes came as he launched his policies on gender equality with a promise to have a 50% female shadow cabinet and "work towards" ensuring half of Labour MPs are women.
Policies in Mr Corbyn's Working With Women document include forcing companies to publish equal pay audits and moving towards universal free childcare.
Appearing on BBC Radio 4's Woman's Hour to discuss his ideas, the MP was also asked about the discussion prompted on Mumsnet by a user who asked: "Anybody else think Jeremy Corbyn is very sexy?"
"This is the most embarrassing thing I've ever heard," he said. "I had a bit of a chuckle about it, but I'm actually a bit embarrassed, to be quite honest."
However, his embarrassment did not prevent him from appearing later alongside fellow candidate Liz Kendall in a webchat on Mumsnet, in which he agreed that she and Yvette Cooper had been subjected to damaging sexist attitudes during the leadership campaign.
"I think people should be judged on the policies they're enunciating and not on levels of bad attitudes or abuse that are heaped upon them by anybody else and some of our popular media," said Mr Corbyn. "Actually, I don't do personal, I'm more interested in ideas and politics."
Speaking on Woman's Hour, Mr Corbyn criticised the media for focusing on personalities rather than policies in a race which has already seen Chuka Umunna withdraw his candidacy because of the scrutiny directed at family members.
"It is very sad that some sections of the media are incapable of engaging in any of this at a political level and engage in it solely at a level of personal intrusion and personal abuse," he said. "Does it hurt those around me? Yeah, it does."
In his new document, Mr Corbyn called for an "urgent" end to Government cuts in public services and welfare, which he argued are pushing women and families in to poverty.