Labour’s powerful ruling body, the NEC, decided to take the contractor’s passes away after members raised concerns about Carillion, which is facing court cases from workers over alleged blacklisting.

General union GMB, which has been campaigning against blacklisting, has now taken the space that was allocated to Carillion.

The union said it would use the stand to ask Labour Councillors from across the UK to follow the lead of the Welsh Government to exclude firms using blacklists from public contracts.

GMB claims that Carillion checked at least 14,724 names with the Consulting Association in the period from October 1999 to April 2004, making it one of the industry’s bigger users.

Paul Kenny, GMB General Secretary, said, “The Labour Party must be applauded for kicking Carillion out of the exhibition hall at its Conference.

A spokesman for Carillion said it was ‘surprised and disappointed’ by the decision.

He said: “Carillion has been open with MPs and the public in talking about its historic involvement with the Consulting Association, which we proactively stopped in 2004.

“We struggle to understand how blocking discussion on difficult issues helps resolve them.

“It is a backward step and a missed opportunity for members to meet a major UK employer working in vital public services.”

He added: “Our Chief Executive, Richard Howson, has expressed regret for the past involvement of a former subsidiary, but it is important to understand that Carillion has never been involved with activity that was illegal.”