MPs have called for a leading construction company refurbishing Big Ben to be stripped of its £29 million contract because of its "disgraceful role" in blacklisting workers.

During a Westminster debate, the SNP’s Chris Stephens denounced the decision to award the contract to Sir Robert McAlpine as a scandal.

The backbencher added his voice to demands for the UK Government to establish a public inquiry into blacklisting, which he branded an “odious practice,” in order to expose its true extent.

The Glasgow South West MP noted that, despite employment law being reserved, the Scottish Government had issued regulations so that any company found guilty of blacklisting workers was banned for bidding for public sector contracts.

He referred to a previous inquiry into blacklisting by the Commons Scottish Affairs Committee, at which company director Calum McAlpine was “forced to admit the company had used the black list to vet workers on the Olympic stadium”.

Mr Stephens told MPs: “It is most shocking…that they have been awarded a £20m contract for Big Ben, a contract to refurbish one of the most iconic buildings in the country, which symbolises the seat of power and London as a global destination

“I am calling today for McAlpines to be stripped of that contract. It’s an absolute disgrace and scandal that they were awarded that contract in the first place.”

The SNP MP urged the Government to look at what the Scottish Government had done in regard to looking at companies in the public sector, which had been engaging in blacklisting.

He added: “It signals bad faith that one of the main perpertrators of this conspiracy, and blacklisting is a conspiracy, are accessing public money to boost its profits.”

As the Westminster Hall debate took place, GMB members joined a protest in Parliament Square over the awarding of the Big Ben contract, which the union said was "scandalous".

Labour’s Chukka Umunna, who sponsored the debate, suggested MPs should be less concerned at the loss of the bongs on Big Ben than by the fact McAlpines, implicated in blacklisting, had “bagged” the refurbishment contract.

“There must be consequences when you bid for public contracts and you are found to be involved in these kind of practices,” declared the London MP. “Why on earth are Sir Robert McAlpine to be awarded this contract to fix the bongs on Big Ben…given their disgraceful role in blacklisting?” he asked.

Jack Dromey, the Shadow Minister for Labour, said: “Blacklisting is illegal but the law is not strong enough. No one has been punished, no director has ended up in the dock. It is happening right now in big companies. It is time to blacklist the blacklisters.”

Margot James, the Business minister, insisted the Government took blacklisting very seriously and hoped it had become a thing of the past. She said regulations in place were robust enough to stop the practice from occurring but if there were claims of it happening, then she wanted to hear them.

“Blacklisting of trade union members and activists is absolutely unacceptable and has no part to play in modern employment relations,” she declared.

In response to the issue of the Big Ben contract, Ms James told MPs she would “further consider” calls for companies involved in “disreputable or illegal” practices to be excluded from public contracts.

Last year, a number of leading construction companies, including Sir Robert McAlpine, made an out-of-court settlement over blacklisting claims. Some £50 million was paid in compensation to more than 700 workers with union legal costs estimated at £25m.