The Serious and Organised Crime Agency (Soca) has withheld from MPs information about the criminal activity of large British firms, it has been alleged.

Soca uncovered illegal activity by insurance and telecoms companies, legal firms and wealthy individuals who paid private investigators to hack computers and steal information from rivals and private individuals.

According to a report leaked to the Independent, Soca compiled a report into private investigators but took no action into the illegal activity they discovered, effectively allowing it to continue.

The report – finished five years ago – was supplied to the Leveson Inquiry into press ethics in 2012 but it was not publicised. Members of Soca later did not mention their report when they appeared before the House of Commons home affairs select committee.

According to the Independent, one of the hackers cited in the report said that 80 per cent of his clients were non-media companies and 20 per cent media. Media use of private investigators has been subject to extensive investigation and prosecution by the Metropolitan Police as a result of the News of the World phone-hacking scandal.

Tom Watson, a Labour MP who sits on the home affairs committee, said that he will be writing to the committee chairman. "I shall be writing to the home affairs select committee as I think this is the subject area they would like to look at having recently produced a report examining the role of private investigators.

"Soca chose not to volunteer any information previously and I'm sure the committee will want to find out what they knew and did not know. I find it extraordinary that the head of Soca who would have had full knowledge of committee's inquiry felt he should not contribute information."

A spokesman for Soca said that they had produced a confidential report on the issue of licencing 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."