Yvette Cooper is facing claims that her campaign to be Labour leader is running out of steam as high-profile MPs flock to rival Liz Kendall.
Cooper, who has been in parliament for 18 years, has won private support from at least 35 Labour MPs in the contest – enough to get on the ballot paper in the leadership contest.
But Labour HQ sources have told BuzzFeed News she has been disappointed by the failure to win over some high-profile MPs she had apparently banked on for support, such as shadow Northern Ireland secretary Ivan Lewis.
He has joined fellow frontbenchers Chuka Umunna, Tristram Hunt and Emma Reynolds in backing Liz Kendall, who was first elected in 2010, for the top job.
One Labour staffer, who does not work directly for any of the candidates, told BuzzFeed News: "Yvette's camp are rattled. They thought they could win over many of the women and New Labour-ites but Liz is getting to them first.
"Liz has got all the glamorous people behind her, like Chuka and Tristram. Andy's got others like Rachel [Reeves] and Dan [Jarvis]. There's a tiredness to Yvette's campaign. She doesn't really know why she's standing; it's just something she thinks she should do."
Another individual who has long known Cooper said she had so far failed to set out what she really stands for: "She was loyal enough to Blair, she was loyal to Brown, she was loyal enough to Ed Miliband. Will the real Yvette Cooper please stand up?"
To counter whispers that she has not made plain why she is running for leader, Cooper will make a major speech on Friday setting out where she stands on a range of issues.
Cooper is among four candidates hoping to be Labour's next leader following the party's devastating defeat at the general election.
Andy Burnham remains the bookies' favourite but Kendall has shot into second place in recent days, followed by Cooper and Mary Creagh.
Cooper's team denied that her campaign lacked momentum. A spokesperson said that while Cooper had support from MPs across the country – including Ian Austin and Emily Thornberry – politicians were not her "sole focus".
"It's important that the PLP [Parliamentary Labour Party] are involved but they are 232 votes out of hundreds of thousands," they said. "Our focus is really moving outside of Westminster and we hope that other campaigns follow because we do need a debate with voters."
Nominations in the Labour leadership race close on 15 June, with the winner announced on 12 September.
They will be elected under a new "one member, one vote" rule brought in by Ed Miliband last year. In the past, a third of the vote was decided by trade unions, a third by Labour MPs and MEPs, and a third by Labour members.