Labour risks becoming the "new nasty party", leadership candidate Angela Eagle has warned.
Ms Eagle borrowed Theresa May's famous 2002 description of the Conservatives as she called for action from the Labour leadership on "abuse, misogyny, homophobia (and) anti-Semitism" affecting the party.
Her call came shortly after Labour's National Executive Committee suspended all local party meetings amid reports of intimidation, bullying and threatening behaviour, and just days after a brick was thrown through her own constituency office window in Wallasey on Merseyside.
The party has suspended its constituency party in Brighton and Hove and annulled the results of a recent election following accusations of abusive behaviour, an improper ballot and entryism by far-left activists.
Turning Jeremy Corbyn's "kinder politics" catchphrase against him, Ms Eagle said that Labour needed "a kinder politics in reality" and must not end up "in the gutter".
The former shadow business secretary, who quit the shadow cabinet to launch her challenge to Mr Corbyn's position, asked party members at a social event in Wolverhampton: "What attracted you to the Labour Party in the first place? I'm guessing it didn't involve abuse, misogyny, homophobia, anti-Semitism and the opportunity to picket Labour events ...
"The Labour Party can't become the new nasty party for women, or indeed for anyone else. It's a place where everyone should play a part. Men and women. Old and young. Black and white. Gay and straight ... We need a kinder politics in reality, which is why I've called on the leadership to not just call out such behaviour but to take action too.
"I've launched a campaign called 'Keep It Comradely'. We should be proud of the Labour movement and what we have achieved. I don't want Labour in the gutter. I want it in power."
Ms Eagle said that ordinary party members had been "let down by those at the top of the party", who had failed to make progress at local elections, delivered a "lacklustre and half-hearted" EU referendum campaign and lost the faith of many voters who "look at Labour and think we don't get it".
Her comments came as her rival for the Labour leadership, Owen Smith, won the backing of one of Mr Corbyn's most loyal MPs.
Cardiff Central MP Jo Stevens was one of 40 MPs who refused to back a no confidence motion in Mr Corbyn. But she has now told supporters she will back Mr Smith in the leadership contest.
In an email to party members, Ms Stevens wrote: "During the past two weeks it has become painfully obvious that we have been unable to fulfil the very basic day to day operation as the official opposition in Parliament.
"We cannot present ourselves as a government in waiting without leadership and a leadership team that commands the respect and support of not only members....but Labour voters and potential Labour voters."
Despite dozens of resignations from his front bench and a 172-40 vote of no confidence from his MPs, Mr Corbyn has refused to step aside. He retains the support of Labour's big union backers and earlier this week won the right to feature on the leadership ballot paper without having to clear the hurdle of collecting nominations from 51 MPs or MEPs.
But shadow Wales secretary Paul Flynn told Politics Home magazine his leadership may have "passed the tipping point".
"It was understandable when the born again Blairites were plotting against Corbyn, and then it increased into the coup last week, the avalanche," said Mr Flynn. "But it gets to a tipping point when it's taking in the new left. You wonder if it's possible to rescue it from there."
Mr Smith postponed the launch of his leadership campaign, scheduled for Friday, following the previous night's terror attacks in Nice.
The Labour Party declined to comment on the suspension of its Brighton and Hove branch, saying only: "We do not comment on private meetings or ongoing investigations."
A spokesman added: "No abuse of any kind by Labour Party members or supporters is tolerated. Any complaints of bullying or intimidation and allegations of misconduct are always taken very seriously.
"We would encourage anyone who has been the subject of threats to inform the party and contact the police."