A leading employment lawyer has called on the Metropolitan Police to reveal their role in the alleged blacklisting of construction workers and environmental activists in what the GMB Union are calling the “greatest employment scandal” of the past 50 years.

In a statement to the Press Association, the GMB said the secret file had the details of more than 3,200 mainly building workers and was used by 44 companies to vet potential employees.

Solicitor Michael Newman, from the law firm Leigh Day, who are representing the GMB, said:

“The secret blacklisting and sharing of personal details by Special Branch officers in order to potentially deny employment to over 3,000 people is a deeply troubling allegation.

“In order to establish how this happened and who was involved we have submitted a Freedom of Information Act request to the Metropolitan Police, who oversee Special Branch. Within this request we have asked to see the Metropolitan Police’s internal report into the matter along with the records of any related meetings and emails.

“Once we have this information we will discuss the legal options available to our clients.”

The issue had first come to light in 2009 when the Information Commission's Office seized a database from an organisation called the Consulting Association, revealing details of 3,213 construction workers and environmental activists, used by 44 companies to vet new recruits.

The GMB claim that workers on the list were denied employment. Scotland Yard said allegations about police involvement with the blacklist will be fully explored during a current public inquiry into undercover policing.

Justin Bowden, National Officer of the GMB, said:

"3,213 secretly blacklisted construction workers and environmentalists deserve to know exactly what role the police played in supplying information about them to the construction companies.

"They have a right to know who, what, where, when and why information was shared between the police and the construction companies.

"It is now time for Scotland Yard to make public everything that they did and come clean about their part in the greatest employment scandal of the past 50 years."