Some of the UK's most respected industries routinely employ criminals to hack, blag and steal personal information on business rivals and members of the public, according to a leaked secret report.

The Serious Organised Crime Agency (Soca) knew six years ago that law firms, telecoms giants and insurance were hiring private investigators to break the law and further their commercial interests, the report reveals, yet the agency did next to nothing to disrupt the unlawful trade.

It is understood that one of the key hackers mentioned in the confidential Soca report admitted that 80 per cent of his client list was taken up by law firms, wealthy individuals and insurance companies. Only 20 per cent was attributed to the media, which was investigated by the Leveson Inquiry after widespread public revulsion following the phone-hacking scandal.

Soca, dubbed “Britain’s FBI”, knew six years ago that blue-chip institutions were hiring private investigators to obtain sensitive data – yet did next to nothing to disrupt the unlawful trade. The report was privately supplied to the Leveson Inquiry into press ethics in 2012 yet the corruption in other identified industries, including the law, insurance and debt collectors, and among high-net worth individuals, was not mentioned during the public sessions or included in the final report.

Tom Watson, the campaigning Labour MP, said: “What is astonishing about this whole murky affair is that Soca had knowledge of massive illegal invasions of privacy in the newspaper industry – but also in the supply chains of so-called blue-chip companies.

“I believe they are sitting on physical evidence that has still not been disclosed fully to forensic investigators at the Metropolitan Police. The law should also be rigorously applied to other sectors that have got away with it.”

One of five police investigations reviewed by Soca found private detectives listening in to targets’ phone calls in real-time. The report said a “telephone interception specialist manufactured several devices which were physically attached to the target’s landline at the relevant signal box by a British Telecom-trained telecommunications engineer.”

During another police inquiry, the Soca report said officers found a document entitled “The Blagger’s Manual”, which outlined methods of accessing personal information by calling companies, banks, HM Revenue and Customs, councils, utility providers and the NHS.

“It is probably a good idea to overcome any moral hang-ups you might have about ‘snooping’ or ‘dishonesty’,” it read. “The fact is that through learning acts of technical deception, you will be performing a task which is not only of value to us or our client, but to industry as a whole.”

The Independent understands that one of the key hackers mentioned in the report has admitted that 80 per cent of his client list was taken up by law firms, wealthy individuals and insurance firms while only 20 per cent of clients were from the media.

A security source with knowledge of the report – codenamed Project Riverside – said clients who hired corrupt private investigators included:

* a major telecoms company;

* a celebrity who broadcasts to millions of people every week;

* a well-known media personality, who hired a private investigator to hack his employee’s computer as he suspected she was selling confidential information to business rivals;

* a businessman who hired hackers to obtain intelligence on rivals involved in an ultimately unsuccessful £500m corporate takeover.

A company which was owed money by property developers also hired private detectives to track down the firm’s family information, detailed transactions from four bank accounts, information from credit card statements and an itemised mobile phone bill. The company paid £14,000 for the information.

However, the most common industry employing criminal private detectives is understood to be law firms, including some of those involved in high-end matrimonial proceedings and litigators investigating fraud on behalf of private clients.

Illegal practices identified by Soca investigators went well beyond the relatively simple crime of voicemail hacking and included live phone interceptions, police corruption, computer hacking and perverting the course of justice.

Despite the widespread criminality uncovered by Project Riverside between 2006 and 2007, none of the suspects identified in the report was charged with criminal offences until after the phone-hacking scandal four years later.

Police were finally forced to act after the scandal that caused the closure of Britain’s biggest-selling newspaper, the resignation of two Scotland Yard police chiefs and the establishment of the Leveson Inquiry.

The Labour MP Keith Vaz, chairman of the Home Affairs Select Committee, said: “I am deeply concerned about these revelations. I will be seeking an explanation from Soca as to why this was not told to the Committee when we took evidence from them about the issue of private investigators.

“It is important that we establish how widespread this practice was and why no action was taken to stop what amounted to criminal activity of the worst kind.”

The former News of the World deputy editor Neil Wallis added: “Until The Independent told me about this, I had not the slightest clue of the scale of illegal information theft going on among our supposedly respectable professions. Did Lord Justice Leveson only conduct his inquiry into 20 per cent of the problem?”

The Soca report, which contains “sensitive material” that may be subject to “public-interest immunity” tests – effectively banning it from ever being published even if it were disclosed during legal proceedings – found private investigators to be experts at “developing and cultivating useful relationships” through “socialising with law enforcement personnel”. One particular method identified was to become a member of the Freemasons, which has been repeatedly linked to corruption in the police and judiciary.

Victims of computer hacking identified by Soca – who suffered eBlaster Trojan attacks which allowed private investigators to monitor their computer usage remotely – include the former British Army intelligence officer Ian Hurst. He was hacked by private investigators working for News of the World journalists who wanted to locate Freddie Scappaticci, a member of the IRA who worked as a double-agent codenamed “Stakeknife”.

Another victim was Derek Haslam, a former Metropolitan Police officer who was persuaded by Scotland Yard to go undercover and infiltrate Southern Investigations, a private detective firm, as a “covert human intelligence source”.

A Soca spokesman said: “Soca produced a confidential report in 2008 on the issue of licensing the private investigation industry. This report remains confidential and Soca does not comment on leaked documents or specific criminal investigations. Information is shared with other partners as required.” Scotland Yard declined to comment.

Belfast Telegraph