Last year the Associated Examining Board merged with the Northern Examinations and Assessment Council and the City and Guilds organisation.
But now it is under fire from a separate arm of Government for taking the lion's share of the market. The Assessment and Qualifications Authority has 53 per cent of the UK's GCSE market, 52 per cent of A-levels and 52 per cent of national vocational qualifications awarded in the workplace.
The enforcer was David Blunkett, the Education Secretary, who wants as few examination boards as possible. In the 1980s there were more than 20 offering O-levels, CSEs and A-levels. Now there are three "unitary" bodies But now the OFT has taken the first step on the route to an investigation by the Monopolies and Mergers Commission. Last month it asked the AQA for its views on its compliance with the Fair Trading Act 1973.
A spokeswoman for the OFT said that most preliminary inquiries do not lead to an MMC investigation. The OFT is obliged to act if, as the result of an acquisition or merger, an organisation controls 25 per cent of the market or has Pounds 70 million of assets.
The Department for Education and Employment said:"We stand by the decision to encourage the creation of unitary bodies." The AQA refused to comment.