Costain warned earlier this month that £22m in outstanding payments were in doubt after main contractor AE&E Inova said its Swiss parent company had entered administration.

Costain held a series of talks with AE&E Inova, which continues to trade, and was promised a £2.6m payment would be made on December 10.

But in a Stock Exchange update this morning Costain said: “The £2.6 million stage payment due to Costain on Friday 10 December has not yet been received.

“Costain is maintaining an active dialogue with AE&E Inova as the Swiss-based company seeks to secure its future and meet its obligations and, in addition, Costain continues concurrent and positive discussions with Cory Environmental, for whom the Belvedere facility is a development project, regarding payments and completion of the project.

“AE&E Inova is continuing to trade and has advised Costain that in relation to their search for a new investor it has “binding offers from well-known strategic investors”.

“In addition they have indicated that “they are working to an aggressive timetable” and “are confident that they will now be able to secure their future”.