Labour and other parties have a responsibility to stamp out vitriolic online abuse that is threatening to stifle democracy and all too frequently targets women, Yvette Cooper has said.

Following Jeremy Corbyn’s declaration that he intends to lead a clean campaign over the coming months, the former shadow home secretary said this was welcome but “not enough” given that her female colleagues were being subjected to a torrent of online threats and misogynistic and racist abuse.

“Labour has a responsibility to party members, staff, elected representatives and supporters to ensure they are not subject to a baying mob online or offline,” she said. “Some of the awful abuse – including death threats – aimed at Labour members, Labour MPs and at our leadership has been from the far right or from those who hate the Labour party. But there has also been unacceptable abuse from within the party too. We cannot allow this to poison our party.

“I am ashamed at how slow my party is still being to act against online abuse. Vitriolic abuse is damaging democracy. Intimidation is stopping people engaging in public debate. The internet should be making it easier to get involved – we cannot allow it to magnify this hate instead.”

Cooper, who will open a conference organised by the movement Reclaim the Internet on Monday in London, called for all companies, political parties and institutions to take tough action. She has written to Iain McNicol, Labour’s general secretary, with a proposed code of conduct that calls for members to be expelled if they have engaged in abuse, intimidation or harassment online.

She is also calling for social media companies to take tougher action and be more transparent, and for police to have more training in how to investigate online crimes.

Last week John Nimmo, a convicted online abuser, pleaded guilty at South Tyneside magistrates court to sending a letter or communication to the Labour MP Luciana Berger which caused anxiety or distress. He was remanded in custody and will be sentenced on Wednesday.

Berger contacted police after receiving threats, including a message saying she was going to “get it like Jo Cox did”. Nimmo was previously convicted in January 2014 and jailed for eight weeks for online abuse of the Labour MP Stella Creasy and the feminist campaigner Caroline Criado-Perez.

Berger has repeatedly been subjected to abuse, often referencing her Jewish heritage, and she has increased the security at her home.

Last week female members of Labour’s ruling body, the NEC, said they had been subjected to death and rape threats online, as well as offline abuse including having their windows and cars smashed, in the run-up to a vote on whether Corbyn should be included on the ballot paper in the Labour leadership contest.

Reflecting comments made by the Conservative MP Maria Miller, Cooper said there was evidence that the levels of online abuse were increasing the scale of hate crimes offline. She highlighted the fivefold increase in hate crime since the Brexit referendum.

“All political parties need to set new standards for their own members and show they won’t tolerate abuse or hatred,” she said.

The Reclaim the Internet conference will be attended by leading figures from Facebook, the Crown Prosecution Service, and a cross-party group of MPs.

