Chris Grayling was facing questions over his record as lord chancellor today, after sources told Politics.co.uk he appeared to personally intervene in a prison sex inquiry.

The inquiry into sex in prisons was intended to investigate how common rape or consensual sexual relationships were behind bars, but sources close to the investigation said they were prevented from speaking to prisoners by the intervention of the lord chancellor.

Sources say Grayling's reaction to the inquiry was to say: "Prisoners aren't going to have sex on my watch."

The Epsom and Ewell MP is even reported to have banged his hands on the desk during a meeting with officials and shouted that he would not tolerate prisoners having sex, despite the fact that the inquiry was intended as a fact-finding mission rather than a campaign project.

The justice secretary is also understood to have demanded that condoms be removed from prisons and was only stopped when officials stepped in to advise him on the devastating public health implications of the move.

The inquiry into sex in prison was initiated by the Howard League for Penal Reform and had a distinguished board of experts on its panel, including leading criminologists, public health advisors and barristers.

Labour MP Fiona Mactaggart and former Tory solicitor general Edward Garnier were also serving as commissioners.

Sources close to the inquiry told Politics.co.uk it was greeted warmly by officials under the tenure of Ken Clarke, but that relations became "chilly" once Grayling was shuffled into the roles of lord chancellor and justice secretary.

Organisers said they were happy to make any changes the National Offender Management Service wanted and were able to demonstrate a long track record of producing authoritative reports by working with people in prisons.

The application to speak to prisoners was then delayed while it was "with ministers" before being rejected.

The inquiry has since proceeded with investigators questioning former prisoners, but the results are not expected to be as valuable.

The refusal to allow investigators into prisons means the government will still not have a clear idea of the extent of rape behind bars, which could be a more significant problem than authorities had previously recognised.

Some sources even indicate that the intervention may have been intended to suppress information about sexual assaults which take place behind bars and the suicides and self-harm which often follow.

Worrying but unconfirmed reports suggest that in the worst cases prison staff can be complicit in sexual assaults, demanding that inmates provide sexual services under coercion.

There is also a dearth of information about consensual sexual relationships in prison.

The difference between consensual and non-consensual sex in prison is very difficult to assess. Penal experts say doing so is all-but impossible without an open, confidential conversation with prisoners themselves.

Under current guidelines, prisons make condoms available to inmates under prescription from doctors, in an effort to prevent the transmission of sexually transmitted diseases.

Grayling's reaction to the issue is understood to be based on his desire to create a "Spartan" regime in prisons.

In 2012, a source close to the justice secretary told the Telegraph: "We don't want and we will not accept prisoners replicating cosy, domestic relationships by being able to share cells in our prisons."

Ironically, the report's authors expected to find that rape was comparatively rare in British jails. It is thought to be a much less common problem than in the US, where the federal government had to intervene with the Prison Rape Elimination Act last year.

There are figures available for reported sexual assaults in prison but these only reveal the information that makes it to the prison authorities.

The real problem will almost certainly be more extensive. Experts believe many sexual relationships in prison may appear consensual but in fact involve a very high degree of coercion.

Unfortunately prison authorities will be largely unaware of the extent of the problem and unable to spot warning signs among inmates because the investigation has been hamstrung by officials.

The last Howard League in-prison investigation, which was granted access by the outgoing Labour government and the coalition, was on veterans in the penal system.

It was praised by Tory MP Rory Stewart during the launch event for his own Grayling-backed inquiry.

Grayling addressed that meeting but observers say he quickly left the room once the author of the report took to the stage and celebrated the efforts of the Howard League.

The justice secretary considers the Howard League a left-wing pressure group and has been quick to attack it during the ongoing prisoner book ban row.

The Howard League has since published an interim report into sex in prison and is currently speaking to former inmates before compiling a final report.

The Ministry of Justice would not comment on this story but referred us to the National Research Committee's reasons for rejecting the application, which are published in full below: