The Office of Fair Trading investigations are too long and it should set itself deadlines, the National Audit Office has said.

The criticisms come a week after the OFT was urged to speed up its investigation that could lead to a full review of the grocery market.

In a report the NAO argues that six of the OFT’s 37 investigations have taken more than three years and one had taken more than five years.

Edward Leigh, chairman of the Commons Public Accounts Committee, said: “The OFT must do more to stop its cases from dragging on in this way. Although the OFT has had some notable successes, its investigations are small in number and long in length.”