Southampton’s civic chiefs have pledged to seek written guarantees from suppliers and partners that they do not use ‘blacklisting’.

The practice involves keeping secret files on people who are deemed to be trouble-makers because they have taken part in trade union activities, or have simply asked for basic health and safety regulations to be put in place during dangerous jobs.

The list is secretly checked by employers and agencies in order to exclude blacklisted workers from employment.

But Southampton’s ruling Labour group have now vowed to check that businesses do not use the practice, before they agree to work with them.

It comes after Unite general secretary, Len McCluskey, visited the city to campaign on behalf of blacklisted worker John Wheeler.

Fawley refinery rigger, Mr Wheeler, has been unable to find work in the construction industry for 20 years, thanks to a file held on him by the now defunct Consulting Agency (CA).

Construction firms previously paid money to subscribe to the CA list – and discriminated against those that were named.

It is estimated that around 50 people from Hampshire were among those blacklisted.

Mr McCluskey said: “The Consulting Association and the employers who used it destroyed the livelihoods of thousands of innocent working people like John. “But it is because of people like John, who have been treated terribly by their employers and the courts, that Unite vows to continue the fight for justice against blacklisting.”

Councillor Andrew Pope, who put forward the motion against blacklisting, said: “Blacklisting ruins lives. It is discriminatory. The victims do not even know that they are on the blacklist. Some who were blacklisted are now dead.

“Can you imagine the impact on a worker’s family and life if they could not work because they once raised concerns about asbestos?

“Blacklisting is an unethical and inhumane practice, and as a council we deplore it.”