Stan Hardy gave evidence to MPs on the Scottish Affairs Select Committee’s blacklisting investigation last week.
He told the committee, “Blacklisting has operated since the pyramids.
'There is not a HR professional in the world that does not have a filing cabinet that says ‘do not employ’”.
Hardy is a former director of the right wing Economic League.
When that collapsed he formed another company, Caprim, and continued to spy on campaigners, trade unionists and socialists.
Hardy claimed that Caprim did not hold records on individuals and was not involved in blacklisting.
Yet it held information and knowledge on campaigning groups and “far-left” political parties, that were seen as a threat to businesses.
Ian Kerr, who died last December, ran a blacklisting firm called the Consulting Association (CA).
The committee published CA documents showing membership and usage charges by 34 contractors from 1996-7 until 2009.
Sir Robert McAlpine was the largest user during the period covered, with a total spend of £220,000.
Five women environmental activists have found their names on the blacklist.