Andy Friend, John Laing's chief executive, will step down in the autumn after seven years at the company.

Friend will be replaced by Adrian Ewer, who has been finance director at Laing since 1999 and who played a key role in transforming the company into a PFI specialist after it sold its building business to O'Rourke for £1.

The company said at its annual meeting that Friend was leaving to "pursue new challenges" but was not joining a competitor. Ewer will take on the top job on 1 June.

Bill Forrester, the chairman of Laing, said in his annual statement that its Chiltern Railways subsidiary was likely to lose money in the current year.

Problems arose when a tunnel being built over a rail line at Gerrards Cross in Buckinghamshire collapsed. Tesco has admitted liability for costs and losses.