Nigel McArthur had worked at the company for nearly ten years and had nearly 40 years’ experience in the construction industry.

Balfour Beatty tendered in 2014 for an £18.5m project at Callaghan Square in Cardiff which would be paid for out of public funds by the Welsh Government.

But McArthur believed Balfour would be making greater profits than declared to the client by not submitting the lowest quotes received by subcontractors to the Welsh government.

He raised concerns internally through the company’s whistleblowing procedures but claims he was subsequently bullied.

McArthur resigned in February 2015 and began a claim for constructive dismissal.

Balfour Beatty admitted his claim in November 2015 and the compensation judgement of £137,000 has now been handed down by the court.

Balfour Beatty said: “In the employment tribunal proceedings, Balfour Beatty did not contest Mr McArthur’s claim for unfair dismissal and is paying compensation to him as assessed by the Court.

“We accept that we failed to properly support our employee following concerns he raised, which resulted in him feeling it was necessary to resign.

“Balfour Beatty encourages its employees to report workplace concerns they may have and we have the tools in place to support them in doing so.

“We regret that on this occasion we fell short of the high standards we set for ourselves in this area. We will use the lessons learnt from this experience to provide better support to our employees in the future.

“Balfour Beatty did not behave illegally or fraudulently in relation to the Callaghan Square project.

“Once senior management were aware of the facts regarding the Callaghan Square project, we provided full disclosure to the Welsh Assembly.

“The Welsh Assembly later made a decision not to pursue the project for reasons of their own unrelated to this matter.”

Terry Falcão, employment lasw partner at Stephens Scown who represented McArthur, said: “Nigel has shown immense integrity throughout this case and has had the courage of his convictions to stand up for the truth.

“This case clearly underlines that even though many companies have whistleblowing hotlines and model policies and procedures in place, it remains very difficult for employees who speak out.”