The Office of Fair Trading, the UK's leading consumer watchdog, is preparing to drop as many as 10 of its probes as part of a drive to concentrate on the kind of high-impact competition and business abuse cases where it has more chance of being effective.

The OFT today issued a policy document outlining its approach to future investigations. The watchdog is currently running about 25 inquiries, with some made public but others carried out informally. It plans to reduce that number to a working level of about 15.

Foremost among the OFT's current probes are an investigation alongside the US Department of Justice into alleged price-fixing by British Airways and others of fuel tax surcharges on long-haul flights. It is also examining the ownership of the UK's airports market, currently dominated by Heathrow and Gatwick owner BAA.

Recently, it came down hard on alleged overcharging by credit card providers and referred Britain's grocery market to the Competition Commission for a full-scale investigation.

The policy shift at the OFT follows criticism, including from the National Audit Office, that it has been to slow to act and ineffective at getting results. Today's move comes after the NAO recommended that the OFT publish more details about the way it selects cases to investigate.

In the future, the watchdog will rank potential cases against six qualifying factors. It will only press ahead with formal inquiries if it can establish that is the best-placed body to tackle the problem, if a sufficient number of consumers are affected and if it can be sure its actions can prevent the abuse.

John Fingleton, the OFT's chief executive, said: "The OFT recently announced changes to the way we operate which will allow us to focus on high impact projects and to look more systematically at whole markets and issues.

"We aim to use all the tools available to us to improve markets where they are not operating effectively. Our objective is to make the OFT more efficient and to concentrate our effort on clear strategic goals."

The OFT acknowledged that it was operating with "finite resources" that need to be better concentrated if it is to be more effective in the future.

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