Balfour Beatty is “monitoring” its relationship with a key labour supplier after the £115m King’s Cross project was hit by industrial action.

About 40 workers from subcontractor Hennelly’s, a major supplier to Balfour Beatty, walked off the project last Friday claiming they had not been paid for three weeks. Hennelly’s is a supplier to Balfour Beatty on a series of major projects across London, including Heathrow Terminal 5.

The workers on Balfour Beatty’s King’s Cross project, where the civil engineering division is building a ticket hall for Network Rail, returned to work this week after talks with Hennelly’s’ management. It is understood they have now been paid.

However, a Balfour Beatty spokesperson said that although the issue had been resolved, the company was “monitoring the situation”.

He added that the walk-out would not delay the project as the work was about to enter a new phase.