Interserve has been forced to write off 拢11m, largely because of costs associated with an investigation into accounting irregularities at the company.

The support services company payed 拢8m for the investigation into 鈥渁ccounting misstatements鈥� at its industrial services division, which came to light last September.

It was also hit by a one-off cost of 拢4m associated with the integration of facilities management company MacLellan which it bought last July.

Interserve added that it had made 拢1m from a PFI asset sale in January 2006 and that it had secured contracts and preferred bidder appointments on work worth more 拢1.8bn.