Ian Kerr was chief executive of the Consulting Association which held information used by contractors to vet potential employees.

Kerr was fined £5,000 after pleading guilty to offences under the Data Protection Act following raids on his office by the Information Commmissioner’s Office in 2009.

The raids found information was held on 3,213 construction workers and more than 40 contractors were using his services.

Kerr will be grilled by MPs on the committee as part of their long-running probe into construction’s blacklist.

Victims of the blacklist are planning a protest before the hearing and will “pack the public gallery”.

Blacklist Support Group spokesperson Steve Acheson said: “I will be listening very carefully to the evidence given by Ian Kerr.

“The secret files the Consulting Association kept on me were used to unfairly dismiss me on job after job for no more than raising genuine safety issues.

“The Select Committee should demand that he names names.

“Who were the senior industry figures that paid his wages and orchestrated this vile conspiracy?”

To watch Kerr’s appearance from 2.30 this afternoon click here