The author of the report into the failings of Rotherham Council and the police, Prof Alexis Jay, has been named by the Home Secretary as a member of the panel looking into historic child sex abuse.

The experienced social worker and Scottish government advisor joins Justice Lowell Goddard, a New Zealand Judge, to investigate whether there was an establishment cover up over celebrities and VIPs who were involved in child sex abuse, the Daily Mail reports.

And Mrs May has also agreed to remove any cut-off date for claims which can be investigated by the experts.

In a written statement to MPs, Mrs May said the inquiry, which also includes Druisilla Sharpling, a barrister and part of Her Majesty’s Inspector of Constabulary, Ivor Frank, a barrister specialising in child protection and family law cases and  Malcolm Evans, a professor of public international law, would have ‘access to all relevant information’.

The previous panel had to be scrapped after two chairs appointed by the Home Secretary had strong links to the establishment, including former Home Secretary Leon Brittan.

The panel will be advised by a number of experts in the field of health and education, as well as a psychologist, the statement revealed.

“All panel members will be formally appointed subject to their conflict of interest declarations and the appropriate security checks,” the statement said.

“The two most important changes are the removal of any cut-off date for the work of the inquiry and, reflecting the importance of survivors to the inquiry, the explicit statement that survivors will be able to bear witness to the inquiry and that support will be made available.”

The first inquiry was set up last July to investigate whether public bodies had neglected or covered up allegations of CSE as paedophiles had been operating in Westminster in the 1980s. The inquiry has been put on a statutory footing, meaning its findings will have proper authority.

Alison Millar, from law firm Leigh Day, which is representing dozens of abuse victims, said: “Most of the clients we represent would really welcome the fact that it is now not time limited to 1970, so will be able to investigate abuse in institutions and schools from much earlier.

‘The people who approach us, the people we act for, it’s a variety of situations: It’s schools, hospitals, care settings, children’s homes, foster care placements.

“I am representing some people who allege that high profile people abuse them. We have a large number of clients who say they were abused by Jimmy Savile. But the majority of people have not been abused by some body high profile or famous. It is a residential care worker or teacher.”

Labour crime spokeswoman Diana Johnson welcomed the news, saying it was positive “that the child abuse inquiry is finally on a statutory footing, with a chair and panel who have been properly vetted and appointed due to clear criteria.”

“It is also welcome that the statutory inquiry will now be able to investigate abuse that happened prior to 1979.

“Most of all, it is welcome that survivors, though not represented on the panel, are finally given formal recognition in the remit of the inquiry and there is a pledge to offer survivors support.

A spokesman from the Survivors Alliance Lucy Duckworth, a support group for victims of CSE said, “The new terms of reference and structure give the inquiry wider powers to compel witnesses to give evidence and will uncover the atrocities and cover-ups prevalent in our institutions for decades.”

She added, “Expanding the terms of reference means institutions responsible for trafficking and abusing children outside England and Wales will also now be investigated.”