Britain’s Office of Fair Trading sent the aggregates, cement and ready-mix concrete markets for a prolonged investigation on Tuesday after an initial study raised concerns about the conduct of major firms towards smaller operators.

The OFT said it had identified a number of features that could restrict or distort competition in the industry, which had a combined turnover of up to GBP3.4bn in 2009, and it had referred the sector to the Competition Commission for a detailed investigation.

OFT Chief Executive John Fingleton said: "We are concerned that competition is not working well in these sectors, with underlying features of the market giving rise to persistent concerns.

"Lack of effective competition not only affects the public sector and business customers but ultimately leads to higher prices for consumers too."

The OFT said five major players accounted for over 90 per cent of the cement market, 75 per cent of aggregates sales and 68 per cent of ready-mix production.