Shares in Interserve dived by as much as 27% on Friday, hitting a four year low, after it announced a £70 million exceptional charge linked to plant it is building in Scotland. The support services and construction firm is constructing a waste to energy complex in Glasgow, but the project is costing more than expected. Chief executive Adrian Ringrose said: "Expectations for the UK construction division as a whole have been significantly adversely impacted by a further deterioration in our Glasgow energy-from-waste contract." Interserve shares finished down 16.5 per cent or 64.9p on the day at 329.3p.