Grant Thornton has resigned as auditors to four Dublin based companies owned by Mindgeek, the operator of the world's most visited pornographic website, Pornhub.

The move by Grant Thornton Ireland to resign as auditors to MG Billing Ltd and three other Dublin Mindgeek owned companies, follows allegations of unlawful content on the Pornhub website in December.

Pornhub denied the allegations and less than a week later, it suspended all content uploaded by unverified users.

Asked about Grant Thornton's decision to resign as auditors to Mindgeek firms here, a spokeswoman for Grant Thornton here said: "In light of the serious nature of recent developments, Grant Thornton Ireland have disengaged with the aforementioned client."

"Due to client confidentiality we are unable to comment on the specific nature or mandate of any client engagements."

"We are not in a position to comment any further," the spokeswoman added.

The records show that Grant Thornton resigned as auditors to the four Mindgeek companies on January 13 last with confirmation of the filed documents only becoming available in recent days.

MG Billing Ltd generated revenues here of $1.3 billion between 2012 and 2018.

The Dublin-based company collects subscriptions from premium users for the Mindgeek global porn empire and revenues for 2018 totaled $220.9m - or a weekly average of $4.2 million.

Prior to the controversy, there were over 100 million daily visits to Pornhub and over 3.6bn visits per year.

Along with resigning as auditors to MG Billing Ltd, Grant Thornton has resigned as auditors to three other Mindgeek companies, Nutaku Publishing Ltd, Mirmay Ltd and Liquidum Ltd.

Since 2012, Grant Thornton had provided audit services to a number of Mindgeek companies and also allowed the Pornhub owner to use Grant Thornton's office address as its registered address here.

As part of the move to disengage from Mindgeek, Grant Thornton no longer allows the Mindgeek firms to use the Grant Thornton office address and the new address for the Mindgeek firms is one on Sir John Rogerson's Quay in Dublin.

The bulk of Mindgeek's 1,800 employees are based in Montreal and the company is headquartered in Luxembourg. 

The move by Grant Thornton follows credit card firms, VISA and Mastercard, moving in December to block their customers from using their credit cards to make purchases on the Pornhub website.

On Tuesday, the chief executive of the Dublin Rape Crisis Centre, Noeline Blackwell, welcomed the move by Grant Thornton to resign as auditors to the Mindgeek firms here.

"I welcome Grant Thornton's recognition that there were questions to be asked about the Pornhub company," Ms Blackwell said.

She stated that Pornhub's actions in taking down unverified content shows that even they weren't happy with how the website was operated.

Ms Blackwell added that the move by Grant Thornton "is what you would expect of a company that adheres to certain values and has policies concerning social corporate responsibility, so it is welcome".

Ms Blackwell stated that other audit firms who may be asked to replace Grant Thornton as auditors to the Mindgeek firms here "will all have their own decision to make in relation to this".

"It is in the name, it is not even hidden - Pornhub," she said.

"Within pornography, there are issues around the exploitation of people and those questions will have to be asked by those people who may decide to carry out that audit work in the future."

In recent days, Mindgeek executives have been grilled under oath about Mindgeek's operations by members of the Canadian parliament.

In December, Pornhub strenuously denied the allegations of unlawful content and announced steps to protect against images of abuse, non-consensual activity including a ban on unverified users uploading material.