The number of police officers fighting financial fraud in the City will be boosted by a third next year in a bid to clamp down on money laundering and other crimes in London's financial markets.
The Corporation of London, which governs the City, warned that police were currently too stretched to even investigate some serious cases.
From next year, the body will add 26 anti-fraud police and will work with the Serious Fraud Office to step up the number of cases which can be looked at.
Detective Chief Superintendent Ken Farrow warned the City's reputation could be tarnished by its popularity among criminals.
"We are a magnet for organised criminals who come here from all over the world to attack the banking system," he said.
The police believe Britain's fight against fraud has been hampered by dwindling resources and a difficulty in securing jury convictions in long, complex cases.
The annual cost of fraud is estimated to have skyrocketed to about £14bn, but the number of anti-fraud police has fallen since 1995.
The Serious Fraud Office, which works with local police to probe frauds involving more than a million pounds, cited one case involving a fraud worth up to £70m, where police could not spare one officer to work on the case.
Mr Farrow, who runs the economic crime unit within the City of London's police force, said organised gangs were increasingly infiltrating banks in the UK, applying for back-office jobs with the sole intention of stealing bank records.
He said police had held talks with the British banking industry over the growing problem.