Accompanied by banners, loud speakers and a giant inflatable rat, members of a union staged a protest outside Hendon Town Hall yesterday to raise awareness of blacklisting in the construction industry.

According to union Unite, construction firm BAM Nuttal, which is now bidding for Barnet Borough Council contracts to build schools, has been ending the contracts of workers who were members of trades unions, had raised legitimate health and safety concerns or been involved in some form of industrial action.

Enfield man Frank Morris, 38, who has 22 years' experience in electronics, said he has struggled to find work after raising health and safety concerns while working at the Olympics site in Stratford.

Mr Morris said: “I worked on prestigious projects such as building on Heathrow Terminal 5 and Canary Wharf, but since 2010, I have been unable to get work.

“I have four children under the age of seven and a mortgage. The effect of the blacklisting is devastating, it has ruined my life.”

Mr Morris added he had seen his name on a database owned by the Consulting Association, which led him to believe he had been blacklisted.

According to Unite’s senior organiser for London and Eastern Erkan Ersoy, who led the protest outside the town hall, Bam Nuttal paid more than £38,000 for the Consulting Association to carry out checks on workers between 1996 and 2009.

Mr Ersoy said: “We have evidence 3,200 people across the country have been affected by blacklisting. The majority don’t know why they are unable to get jobs. We’re running a strategic campaign of protests across the country.

"We want Barnet Council to ban companies that have blacklisted workers from all public tenders for contracts.”

Labour London Assembly member for Barnet Andrew Dismore joined a previous protest outside Hendon Town Hall.

He said: “In this day and age blacklisting workers because they have belonged to trades unions is outrageous.

"This is particularly so when they have been dismissed for raising legitimate health and safety concerns.

"It is unfair when someone has participated in trades union activity to find that not only are they thrown out of work just because of that, but they are unable to find further employment because of their trades union activity.

“This is a clear breach of their human rights in that those concerned are given no opportunity to defend themselves or put their point of view fairly. I fully support Unite the Union’s campaign against this appalling practice.

“Contracts for big construction projects should not be awarded to known blacklisting companies.”

A statement from executive board director of BAM Mark Roger states: "BAM does not engage in blacklisting. Blacklisting has no place in the construction industry or any sector.

"BAM has a good reputation as an employer and always tries to maintain good relationships with trade unions in sectors in which it operates."