More than half the companies that have raised funds on the Alternative Investment Market over the past three years have not made money for investors, an analysis by The Times has found.

Some 52 per cent of those that joined London’s junior market in the three years to December 31 2006 are either trading at or below their issue price, or have had their shares suspended. The study covered 802 companies brought to AIM through an initial public offering (IPO) or reverse takeover by the 39 most active AIM stockbrokers.

Of these, 364 were trading below the ir issue price, 21 were unaltered and 28 had been delisted.

The findings are likely to fuel criticism of AIM that, although it has been the most successful growth market in the world in terms of new listings, it has often sacrificed quantity for quality.

Last month, John Thain, chief executive of the New York Stock Exchange, attacked AIM for a lack of stringent corporate governance.

The analysis uses closing share prices from the end of 2006, since when AIM has been rocked by suspension of Torex Retail, the software developer at the centre of a Serious Fraud Office investigation, and Neteller, the online money transfer specialist, of which two former directors have been arrested in the United States and charged with funnelling billions of dollars in gambling proceeds to overseas betting operations.

Less than two years ago, Neteller was the second-largest company on AIM, with a capitalisation of £991 million.

The Times analysis shows that, among brokers raising £100 million or more, Bridgewell Securities has seen a higher proportion of its floats fall below their issue price than any of its peers - 67 per cent. Bridgewell has recently stepped back from AIM to focus on building its client base among FTSE 250 constituents.

The stockbroker with the lowest proportion of underperformers is South Africa’s Investec Securities, with only 14 per cent trading below their offer price.

That marks a turnaround from the dot-com boom, when Investec gained a reputation for floating companies that came into difficulties, such as the collapsed Sportsworld Media.

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