Poor and disadvantaged customers are failing to take advantage of increased competition in energy, telecom and postal markets because of "complex tariffs" and a "lack of easily accessible, trustworthy, relevant information" ministers were warned today.

A report by the National Audit Office, the parliamentary spending watchdog, expressed concern that 46 per cent of gas and almost 50 per cent of electricity was still sold to customers by their original monopoly supplier, in spite of increased competition.