Protests are being held across the country and the TUC – with support from all the main construction unions – is holding a lobby in Parliament calling for the UK’s biggest construction companies to “own up, clean up, pay up”.

The events coincide with a major legal offensive launched by Unite, Britain’s biggest union, on behalf of blacklisted workers. Proceedings against construction employers follow an announcement by the Information Commissioner’s office this week that 1,200 people will be receiving a letter stating that they are on the blacklist.

Richard Arthur, head of Thompsons Solicitors’ Trade Union Law Group, said: “Today the guilty construction companies have no place to hide.

“The law is clear on blacklisting, with four major pieces of legislation covering every aspect of the issue - from it being unlawful to refuse employment on the grounds of union membership, to the right to privacy of personal information and defamation.

“Blacklisting is a shameful practice that has been allowed to contaminate the construction industry for too long.

“We support the TUC in their call to the government to make blacklisting a criminal offence, and ensure there are demonstrable consequences for companies that purposely discriminate thousands of innocent workers.”