Corruption within the Prison Service is rife, according to a leaked report which reveals that there are more than 1,000 officers involved in corrupt practices.

The report, which is the result of a one-year inquiry by the Metropolitan police and the Prison Service’s anti-corruption unit, was leaked to the BBC.

Within it are claims that the corruption ranges from officers accepting cash payments from inmates to have them transferred to less secure prisons to bringing mobile phones and drugs into prisons.

The corruption stems from "inappropriate relationships" between prisoners and staff and there are nearly 600 of these relationships occurring, according to the investigation.

It claims intelligence is received about corrupt officers but often no action is taken to overcome it. One Prison Service manager says that 70 security intelligence reports filed by officers identifying colleagues as corrupt were never referred higher up, and, as a consequence, no action was taken.

The report is the most detailed to emerge on corruption in prisons. It quotes a series of unnamed prison governors and officers, including one who says: "Here corruption is endemic…I’ve identified over 20 corrupt staff, but there may be more."

Another staff member is quoted as saying: "I currently have 10 corrupt staff and I am managing the threat they pose to my prison – positive mandatory drug testing figures are over 20 per cent so it must be staff bringing in the drugs."

Mark Leech, editor of The Prisons Handbook said the report reveals the service is "institutionally corrupt".

"This report reveals that what was claimed to be a few isolated cases of corruption is in fact the tip of a huge iceberg of dishonest practices that has infected the Prison Service nationwide.

"In short, it stands accused of being institutionally corrupt right across the country.

"The report shows that what the Prison Service currently has in place to tackle corruption is woefully short of what is actually needed in order to root out those officers who pose a threat to their colleagues, a danger to the public, and who bring shame on the service as a whole."

A spokesman for the Prison Officers’ Association said that corruption was linked to poor pay and the failure to vet staff properly when they are recruited. Potential prison staff are no longer interviewed, but have to go through a series of role plays.

Tim Newburn, a criminology professor at the London School of Economics who carried out a report on corruption for the Prison Service six years ago, said that corruption was not a small problem which could be easily dealt with.

"This is an institutionalised, widespread set of misbehaviours – albeit by a very small minority of staff - with a significant problem for control, order, discipline and crucially for ethical conduct within the Prison Service," he told Today.

"If professional standards are not being upheld, it is almost impossible to imagine that constructive work can be done in prisons."

But the Prison Service believes the report overstates the corruption issue and relies on anecdotal evidence.

Phil Wheatley, the Prison Service director-general, acknowledged that there was a problem with "bent officers" in the system, but said that the decline in levels of drug use in prison and in the numbers of escapes suggested that the problem was being successfully tackled.

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