OXFORD West and Abingdon MP Nicola Blackwood has said she cannot understand why a report linking blue chip companies to phone hacking was not raised when the Leveson Inquiry was set up.

Miss Blackwood is a member of the Commons Home Affairs Committee that was this week given a list of companies by the Serious Organised Crime Agency – including legal, financial and insurance organisations – that hired crooked private investigators who hacked, ‘blagged’ or stole individuals’ sensitive information.

But SOCA demanded the committee keeps the client list secret, citing human rights concerns or that it might harm commercial interests of the companies. More than 100 firms are named in the report and one of the investigators said only 20 per cent of his clients were media companies.

Last year, Lord Justice Leveson released the findings of his inquiry into press ethics following revelations that the News of the World had hacked mobile telephone messages, including those of murdered schoolgirl Millie Dowler.

Lord Leveson was shown the SOCA report that revealed hacking was not just limited to certain media organisations, but ruled it was ‘outside his inquiry’s remit’.

But Miss Blackwood said she believed SOCA should have raised the report when the Leveson Inquiry parameters were set.

She said: “SOCA freely admitted in evidence to me that when the uproar about hacking, police corruption and the media led to the Leveson Inquiry they were fully aware that such practices extended well beyond the media.

“SOCA were so worried about this that in their 2008 report they said the course of justice was being perverted by unscrupulous private investigators hired by a number of sectors, including organised crime gangs.

“In a separate report in 2010, SOCA identified private investigators as one of four key sources of police corruption.

“I cannot understand why they did not make these points to the Home Office when the Leveson Inquiry terms of reference were being set in the first place.”

Critics are now demanding SOCA releases the list, while it would also be open to the Home Affairs Committee to ignore the agency and publish the list under parliamentary privilege.

Committee chairman Keith Vaz said: “Those companies or individuals who either instructed private investigators to break the law or did nothing to stop them must be held to account.”

A SOCA spokesman said: “SOCA’s director general Trevor Pearce provided the chair of the Home Affairs Committee with further confidential information on July 22.

“As stated in the DG’s covering letter the information provided does not allege, either expressly or by implication, that the individuals and companies named in it, or any individuals working for those companies, have or even may have committed a criminal offence.”