News of the vulnerability came after the FSA undertook a special investigation of the two business sectors after they were identified as being possible soft targets for money launderers.

The results of the investigation found that while online brokers and spread betting companies had procedures in place to promote compliance with the money laundering rules, 'there were however, several examples of firms not following their own in-house money laundering procedures'.

The FSA report also said: 'This might in turn suggest a shortfall in internal audit procedures or compliance checks.'

Under existing money laundering rules companies involved in regulated activities must appoint a money laundering reporting officer and must abide by the FSA's rules on how to deter the washing of illegal cash through their businesses.

Internal auditors have a major role to play in beating financial crime, a job acknowledged by Richard Nelson, the newly elected president of the Institute of Internal Auditors, who last week pledged in Accountancy Age to 'work hard' to ensure companies improve their risk management practices.

Six areas that are at the greatest risk of being used to launder money have been identified by the FSA. As well as online broking and spread betting the regulator picked on credit unions, independent financial advisers, international banking and domestic retail banks.