The Enquirer understands that the ground engineering contractor, which had operated as a standalone company, is being placed under the control of Balfour Beatty’s major civil engineering division.

Wren, who has been a passionate defender of the specialist subcontractor during his long career at Britain’s biggest construction firm, is understood to have agreed to leave by mutual consent in the on-going shake-up.

A past president of the National Specialist Contractors Council, Wren campaigned hard for fair payment terms for the sector and an end to the retention system.

A friend of Wren’s told the Enquirer: “I gather its all been on very good terms. I think Graham just decided the time had come to move on.”

Piling contractors have hit rock bottom after a tough year where work dried up. The decision to bring the foundations business under the wing of the major civils arm is understood to have been driven by dramatic market changes.

Just before Christmas May Gurney closed its piling business axing 43 jobs because it could see no prospects of recovery.

A Balfour Beatty spokeswoman said: “Balfour Beatty Ground Engineering has been under review for some time.

“The decision to bring it under control of Balfour Beatty Major Civil Engineering will better position the business to meet the challenges of the market and is designed to optimise new opportunities.”

She added that there were no plans to break up Balfour Beatty Ground Engineering or shift the emphasis towards major infrastructure projects.

Stent piling, Branlow mini and micro piling and ground improvement specialist Pennine were all amalgamated into the one business a few years ago.

Stephen Tarr, managing director at Balfour Beatty Major Civil Engineering, will run the foundations business, which will continue to bid for a full spectrum of work from housing to healthcare and offices. He will also oversee the on-going restructuring.

In a separate trading statement today Balfour Beatty said its group-wide order book had risen to £15bn with net cash standing at £400m.

The performance of Parsons Brinckerhoff exceeded expectations with several big efficiency gains achieved at the consultant since it was brought into the Balfour fold.

The firm warned that it had still to see a discernible recovery in the parts of the UK markets which have remained weak.