Crown House, the M&E arm of Laing O'Rourke, is investigating claims that one of its workers on Heathrow Terminal 5, who appeared on Channel 4’s Wife Swap last week, was claiming a lodging allowance at the time.

Electrician Trevor Keddle, from Romford, Essex, appeared on the fly-on-the-wall show last week, despite allegedly claiming accommodation money for the period when the show was filmed.

Keddle declined to comment while the investigation was under way.

The 10-day swap was filmed in August, and the families taking part were paid £500 each.

Keddle’s wife Sharon swapped places for 10 days with an Edinburgh-based woman called Shelia Toft. The show ended after Toft stormed home in fury after claiming that Keddle spent too much time in the pub. Keddle’s wife then threw a glass of water over Toft after she accused her of being a bad mother.

Laing O’Rourke and BAA declined to comment.

Meanwhile, Heathrow Terminal 5 is facing the threat of more action on pay after unions agreed to ballot civil engineering workers.

The unrest came to a head as union Amicus entered into arbitration with BAA over a £1 an hour bonus for steelworkers.

Claims were lodged by civil engineering and steelworkers after electricians were awarded a bonus this year.

Officials from the GMB, T&G and UCATT, which represent civils workers on the project, are making preparations to launch a ballot next month after talks with BAA and contractor Laing O’Rourke failed to reach a successful conclusion.

Meanwhile, unions warned that employers at T5 would be landed with the bill for steelworkers’ bonuses if arbitration between Amicus and BAA failed to find in their favour.

Frank Westerman, Amicus’ national officer, said: “We are confident that we will get the £1 from arbitration. But if the arbitration goes against Amicus, the employers will still have to deal with a dissatisfied workforce without any financial recovery from BAA.”