Amec has wiped off £1bn in construction turnover over the past three years because of its switch from construction to support services.

Chief executive Sir Peter Mason said that the business had scaled down low-margin, high-risk contracting work in favour of engineering and services contracts.

The cut in turnover has not affected the company’s profit levels.

The change in focus may lead to attempts by Amec to switch its listing from the construction and building materials sector to support services, where it would hope to achieve higher earning multiples.

Amec has raised uncertainty in the City, because the change of focus so far has been costly and time-consuming.

Announcing its results for the six months to 30 June, Amec revealed a pre-tax loss of £5.1m, compared with a £27m profit in the same period last year. Turnover dropped 3% to £2.24bn. This was mainly attributable to exceptional costs associated with the sale of its US construction business.

The change in focus may lead to attempts to switch Amec's sector listing

Speculation of a takeover by Bechtel or Fluor Corporation, Amec’s partner in Iraq, was quashed as Mason pointed to the fact that no announcements had been made to the Stock Exchange.

Stuart Siddall, Amec’s finance director, bought additional shares in the company on Friday – which would not be permitted if the firm was in takeover negotiations.

Amec’s share price dropped just 1.5% after the results were posted, in line with analysts’ expectations.

Mason identified UK government spending as a key driver for the business after the 2004 spending review, published in July.