The cost of listing on AIM has continued to increase over the last year to reach an average of 6.7 per cent of all funds raised, up from 6.2 per cent in the previous 12 months, according to research from Birmingham accountancy firm UHY Hacker Young and City law firm Trowers & Hamlins.

The jump in professional costs is despite a 39 per cent fall in the number of AIM IPOs from 462 in 2006 to 284 last year.

Malcolm Winston, partner at UHY Hacker Young, said: "Clearly the fall in IPO activity over the last year hasn’t fed through into lower professional fees.

"Professional advisers are increasing the level of due diligence required for AIM listings and at the moment companies accept that they are going to have to pay more for that.

"The last year has also really proved the point that AIM can work very well for raising secondary finance. Last year £9.6 billion was raised via secondary fundraisings on AIM compared to the £6.6 billion raised by new AIM listings. That is a significant achievement and a real selling point for AIM – no other junior stock market anywhere in the world offers such strong secondary fundraising ability."

However, Mr Winston points out that for companies looking to raise under £10 million the costs of listing on AIM are 18.3 per cent of all funds raised.

Charles Wilson, of Trowers & Hamlins, said: "AIM’s clear and straight-forward approach to regulation has seen it steal a march on other exchanges. However, with competition from copycat markets, AIM needs to be wary of introducing more regulation for companies and their advisers as this may push up the costs of listing further.

"A greater regulatory burden which would probably lead to an increase in costs could result in fewer smaller companies looking to list on AIM – the area of the market AIM originally set out to serve."

The cost of listing on AIM are lower for international companies than for those based in the UK. The average costs of listing international companies was 6.2 per cent of the capital raised, compared to 8.7 per cent for UK counterparts.

Mr Winston said: "Whether a company is based in the UK or overseas is not the sole driver of its costs of listing on AIM. The complexity of the company and its choice of professional advisers will also make an impact."

"A lot of the bigger companies coming to AIM are now from overseas and larger companies tend to spend a far lower proportion of the money they raise on costs than smaller companies."