Jeremy Corbyn is to address claims he has failed to stop his supporters threatening opponents – saying abuse “has no place” within the Labour Party.
More than 40 female Labour MPs have written to the Labour leader saying he has failed to do enough to prevent “disgusting” threats against members.
He is due to condemn abuse in a speech later, as he says a grassroots “social movement” can propel Labour to power.
Meanwhile, leadership rival Owen Smith will promise key party roles to women.
The Pontypridd MP will vow to act on gender inequality – promising two of his four most senior cabinet roles would go to women if he became prime minister.
Mr Smith and Mr Corbyn are launching their leadership campaigns amid complaints that critics of the Labour leader – particularly women – have been subjected to bullying and abuse by his supporters.
A group of female MPs – including former shadow ministers Heidi Alexander, Paula Sherriff and Kerry McCarthy – have written to Mr Corbyn saying intimidation was being carried out “in your name”.
“Rape threats, death threats, smashed cars and bricks through windows are disgusting and totally unacceptable in any situation,” the letter said.
Disagreement in party
Speaking at the public launch of his leadership campaign in Manchester later, Mr Corbyn will say: “I don’t do personal abuse, I don’t respond to personal abuse, I condemn any abuse from others. It has no place in our party.”
Mr Corbyn will say: “I know some people are angry at the actions of some MPs but where we have disagreement in the Labour Party we settle it through democratic means – not coups, not intimidation, and not abuse.”
Simultaneous launch events will take place in cities across the country, including Hull, Newcastle, Cambridge, Bristol, Nottingham, Stoke, London and Cardiff.
Mr Corbyn will acknowledge Labour has “a mountain to climb” if the party is to regain power at the next general election.
However, he will say campaigning as a “social movement” will be the key victory.
“We are a social movement and we will win the next general election only as a social movement.
“Some people don’t get this yet. They think a movement is something instead of parliamentary politics. It’s not. It’s what will make a Labour government possible,” he will add.
MI5’s ‘dark practices’
On Friday, Unite trade union leader Len McCluskey suggested in an interview with the Guardian that the security services could be behind the abuse and intimidation of MPs on social media.
Mr McCluskey said MI5 could be using “dark practices” to “stir up trouble” for Mr Corbyn, arguing that spies had infiltrated trade unions in the past, and that the truth about it had been suppressed for 30 years under the rule on keeping classified documents out of the public domain.
Mr Smith distanced himself from the suggestion, saying at a campaign rally in Manchester: “I’m not sure that’s entirely right.”
Mr Corbyn is facing a challenge from former shadow work and pensions secretary Mr Smith, after Labour MPs overwhelmingly backed a motion of no-confidence in their leader.
The winner of the leadership contest will be announced on 24 September.