Union bosses are today denying claims by Crossrail of an agreement ruling out any blacklisting of workers by tunnelling contractors.

Crossrail insists that Unite has agreed that “no blacklisting has taken place” on its construction.

But the union says that’s not quite right. What it said was “there are no breaches of current regulations” which it believes to be weak.

The controversy first erupted in January when another union, Ucatt, told MPs that workers on a secret blacklist had been barred from the Olympics construction because of union membership or for having raised health and safety issues.

It then emerged that the recruitment consultant involved in blacklisting had also once advised Crossrail—although well before the £15 billion project got going.

Crossrail Chief Andrew Wolstenholme said today: “Unite has made a series of misleading and unsubstantiated allegations. It advised the Scottish Affairs Committee that its evidence was circumstantial and was not sufficient to prove blacklisting.”

He added: “Unite has now issued a joint statement with our western tunnels contractor BFK stating that no blacklisting has taken place.”

But within minutes, Unite issued a counter-statement refuting Wolstenholme’s claim of a clean slate.

The union said: “It is important to correct Crossrail wrongly stating that Unite has said there has been no blacklisting.

“What Unite clearly said is there have been no breaches of the current regulations.

“We believe this indicates the weakness of the current legislation.”

The MPs called for a government inquiry into the allegations.

The London Assembly voted in January to call on Boris Johnson to show what steps had been taken to make sure blacklisting wasn’t being used on Crossrail.

The blacklist was operated by the Consulting Association in 2007 when Olympic job applicants were checked and certain workers were barred, the Assembly was told.

The Association was closed down in 2009 by the Information Commissioner when the list came to light, a year before Crossrail’s first major contracts.