British construction firm Carillion has reported a near 100% jump in interim profits, adding that lucrative public service contracts will boost its results for the full year.

The company said on Wednesday that pre-tax profits for the six months to late June came in at �16.2m ($25.1m), nearly double the �8.2m it reported during the same period in 2001.

Carillion chairman Sir Neville Sims said the company is on track to meet investors' expectations this year.

"With a �5.3bn order book and positive trading outlook, the board expects the group to deliver underlying earnings growth for the full year in line with market forecasts," he said in a statement.

Investors reacted coolly, marking Carillion shares 15p lower to 143p in late afternoon trade, down sharply from the 226p peak they hit in May this year.

Track trouble

Carillion is one of several engineering and construction companies to have benefited from the government's private finance initiative (PFI), under which public service maintenance work is contracted out to private sector firms in the name of greater efficiency.

The PFI, worth billions of pounds, encouraged many investors to snap up shares in Carillion and rivals such as Amey, Capita, Jarvis and W S Atkins.

However, doubts over the way some firms accounted for public service contract revenues and bidding costs has eroded investor confidence in these firms in recent months, depressing their stock market value.

In July, Carillion said changes to the way it accounted for bidding costs would cut its operating profits for the year by about �6m.

Investors are also worried that recent fatal train crashes, possibly caused by poor track maintenance, could affect future earnings from railway contracts.

The crashes, including last May's derailment at Potters Bar, has swelled political opposition to PFI deals, prompting fears that the government could come under pressure to alter or abandon them.

None of the rail crashes occurred on stretches of track maintained by Carillion.