In a letter to the prime minister on Thursday, the activists reportedly called on Johnson to move up the planned rollout of age verification safeguards for web-based porn sites during the Queen’s Speech – an annual royal address to Parliament – scheduled for next Tuesday.

The government had promised to clamp down on web porn in its Online Harms Bill, which is expected to be announced during the Queen’s Speech. But the bill’s provisions are not set to kick in till 2024 – by which time it “will be too late for some women and children,” the letter noted.

They also demanded that Downing Street introduce stringent restrictions on violent and extreme pornography – invoking the high-profile murder of Sarah Everard in March to caution against leaving access to such genres unchecked, according to the Daily Mail.

“While it is too early to talk in depth about what happened to Sarah Everard, it is clear from the outpouring of stories from women across the country following her death that a very large proportion of attacks on women are sexually motivated,” the letter noted.

Among the signatories are Baroness Floella Benjamin, former Digital Minister Margot James, and Javed Khan, CEO of children’s charity group Barnardo’s.

As an alternative to the bill’s proposed timeline, the campaigners called for the enforcement of Part 3 of the Digital Economy Act (2017) – an article that compels “commercial providers of online pornography to have robust age verification controls in place to prevent children and young people under 18 from accessing pornographic material.”

“Given the growing body of research (including research commissioned by the Government) demonstrating a clear association between pornography consumption and a higher incidence of violence against women and girls, the failure to implement Part 3, in the absence of alternative protections, has become unsustainable,” the letter said.

Whitehall has said the new bill will go further than previous legislation, by giving regulatory powers to communications watchdog Ofcom to block access to online services – including social media platforms and search engines – that do not do enough to protect children.

A recent City, University of London survey found that four in five British 16- and 17-year-olds have seen online porn on adult sites as well as on social media. One reason for not implementing age verification as enacted in the 2017 Act has been its inability to cover social media sites.

The letter comes at a time when the government is facing judicial review proceedings on the grounds that it “sought to frustrate the clear will of Parliament to protect children from online harm.”

“Five years is a very long time in the life of a teenager for whom the prevalence of online pornography is having an effect on a daily basis,” said solicitor Paul Conrathe, who has brought the legal action.

“In the meantime, the ease with which those under 18 can access extreme pornographic material online is having significant negative impacts on thousands of children every day. This includes teenage girls suffering sexual harassment at school,” Conrathe told the Guardian earlier this week.