An online petition accusing Pornhub, the UK’s biggest open access porn site, from profiting from videos of rape and sexual abuse has reached over 350,000 signatures.

Pornhub is the world’s biggest porn site and was visited 42bn times last year. It is free to access, with no age restrictions, and raises revenue through advertising and paid-for promotions by porn producers.

The serious allegations levied against Pornhub owner Mindgeek centre on the perceived insufficiency of the company’s safeguarding checks on the 6m videos a year that are posted on the site, many by amateur producers. Over the past year the company has faced multiple accusations that rape and abuse videos were widely posted on the site.

The petition was started by a group called Exodus Cry in the US but is being supported by activists in the UK, where Mindgeek also has offices.

“This is a company that is generating millions in advertising and membership revenue and yet they do not have an effective system in place to verify reliably the age or consent of those featured in the pornographic content it hosts,” said Exodus Cry founder Laila Mickelwait .

Mindgeek – based legally in Luxembourg but with offices in Montreal, London, Nicosia and Los Angeles – denies the allegations made in the petition, insisting that it does have thorough procedures for removing illegal content.

In a statement to the Guardian, Mindgeek said: “Pornhub has a steadfast commitment to eradicating and fighting non-consensual content and under-age material. Any suggestion otherwise is categorically and factually inaccurate.”

But other campaign groups insist that the criticisms of Pornhub are based on evidence of poor practice.

Some of the videos on Pornhub – as on other free to view sites – show extremely hardcore and violent pornography.

Campaigners say that this fact, coupled with the high prevalence of videos promoting sex with young teenagers – “teen” is one of the most popular categories on the site – means there is an urgent need to know for certain that videos are made consensually.

In October last year, a 15-year-old girl who who went missing in Florida was found after videos of her allegedly being raped were uploaded to Pornhub, among other sites. Pornhub removed the video once it was reported to and a man accused of statutory rape in connection with the case is currently awaiting trial.

The site was also criticised for continuing to host videos by the amateur porn specialists GirlsDoPorn – a company that offered girls being featured in porn “for the first and only time” – even as a court in San Diego heard evidence that the videos were made using dishonesty and abuse. The official GirlsDoPorn page was not removed from Pornhub until October, although the court began hearing evidence in August. Their videos were still being found on Pornhub months later.

The men who ran GirlsDoPorn were found liable in a civil case. Two are currently in custody and are now facing criminal charges of sex trafficking while a third has fled the country and is considered a fugitive.

Last month the BBC reported the story of a woman who was raped at 14, with the video of her abuse ending up on Pornhub. She said she then faced a long struggle to have the video removed from the site.

Pornhub insist that they have robust procedures to stop illegal content being posted and defend the material posted as legitimate fantasies protected by freedom of speech.