The infrastructure group issued a profit warning last month after “identify legacy issues” in the UK, US and Middle East would hit profits.

Balfour said today: “The business is focused on managing the historic problem contracts, impacting profit and cash, through to completion.

“As at June 2015, 31 per cent of the historic projects are already at practical or financial completion.

“By the end of 2016 the number of these projects at practical or financial completion is expected to be greater than 90 per cent.

“In the UK there are a handful of very complex projects where the range of potential outcomes could result in a materially positive or negative swing, the most significant of which are in Major Projects.”

Chief executive Leo Quinn said efforts to turn the business around, including a cost-saving target of £100 million by the end of next year, gave him confidence in the future.

For the six months to 26 June, Balfour posted a pre-tax loss of £150m, compared with £58m a year earlier, on underlying revenues that were broadly flat at £4 billion.

Underlying losses at the group’s UK construction business widened to £145m, from £59m last year, after taking provisions on a number of historic building projects.

Leo Quinn said: “Six months in, our Build to Last transformation programme is gaining traction throughout the business.

“We have a new senior leadership team and an organisation re-aligned with key customer sectors. We are on course to meet our 24-month targets for £200 million cash in and £100 million cost out.

“In rising core markets, the group is continuing to win business on better terms across our operations.

“In the last few months the awards of contracts or preferred bidder status for three landmark projects – Bergstrom Expressway in Austin Texas, nuclear new build Hinkley Point C power station electrical package and a UK smart motorway package – is a further endorsement of Balfour Beatty’s leading capabilities.

“Inevitably the headline numbers set out the consequences of the historic issues that are now being tackled.

“However the continuing confidence of our customers in Balfour Beatty’s expertise, the positive response of our people to change, demonstrated by our excellent net cash performance, and the underlying strength of our balance sheet, supported by the Investments portfolio, all reinforce my conviction that over the medium term we can provide our customers, employees and shareholders with superior returns.”