Private investigators working for organised crime gangs have accessed and even deleted law enforcement intelligence records with the help of corrupt police officers and other officials, a leaked report has revealed to the Leveson Inquiry.
The security breaches were uncovered by a Serious Organised Crime Agency (Soca) investigation and set out in a confidential 2008 report obtained by Channel 4 News.
It found examples of unauthorised access to details of current investigations, the location of witnesses under police protection, the identity of informants and the provision of counter-surveillance techniques.
Intelligence records were in some cases deleted, the report said, as part of private investigation activities which "threaten to undermine the criminal justice system".
The operation - codenamed Riverside - found examples of corrupt individuals providing access to the information in four of the five law enforcement operations put under scrutiny up until 2007.
As well as police officers, they included a bank employee, employees in a communications service provider, a public service employee, and a HM Prison Service employee, according to the eight-page report seen by the broadcaster.
The disclosure is certain to reopen calls for private investigators to be regulated and the then home secretary Jacqui Smith is set to be called by MPs to explain whether she was aware of the findings.
Keith Vaz, the chair of the Home Affairs Select Committee, told the programme he would ask colleagues to urgently summon Ms Smith and Soca to give evidence.
"If they knew that there was this widespread deletion of information, and the connection between private investigators and police officers who were involved in inappropriate action, it's very important that they come before the committee and explain themselves, as a matter of urgency," he said.
Soca said it did not comment on leaked reports while the Home Office said it was considering the question of regulation.
Licensing of private investigators was allowed for in 2001 legislation but has not been implemented.
"In the meantime they are subject to the law on intercepting communications like everyone else," a spokesman said.
Among other illicit activities were access to serving police officers' private details and the identity of vehicles used in surveillance as well as checks on what police interest there was in particular criminal outfits.
The former head of anti-corruption at the Met Police, Bob Quick, told the programme: "There were occasions where cases involved officers removing evidence, destroying evidence.
"This was infrequent but when it occurred it was serious. There were indications that relationships existed with private investigators and ex-police officers who were suspected of corruption."