According to KPMG Forensic's Fraud Barometer, over £630 million worth of fraud came to court across 128 cases in the first half of 2008, up from £421 million in 91 cases during the previous six month period.

Banks were the main victims, accounting for over half - £350 million - of fraud to go to court. KPMG says this is more than the total for any previous entire year of the 20 year history of its Fraud Barometer.

The figures were boosted by two big cases - a £70 million attempted fraud within HSBC's securities services division and an alleged attempt by a hi-tech criminal gang to steal £220 million from Sumitomo Matsui's London office. In the latter case the gang hacked into Sumitomo Mitsui's computer network using keylogging software to steal passwords and access the network. They then tried to transfer the cash electronically to 10 separate bank accounts around the world, but the scam was foiled by police.

However, even without these two cases, there was over £60 million of fraud against financial institutions coming to court, compared to just £37 million for the whole of 2007.

Mortgage fraud also rose substantially, with nine cases worth over £20 million in the first half of this year, compared to only 10 cases at £3.7 million for the whole of 2007.

Hitesh Patel, partner, KPMG Forensic, says: "The cases in this period's Fraud Barometer largely predate the credit crunch in terms of when the frauds were committed - the fear is that we will not see the real and full fraud impact of the crunch for another six or twelve months or even more, as businesses start to take a closer look at their operations in this difficult economic climate. The signs are that we could end up seeing some substantial losses being suffered."

The figures also show that two thirds of fraud by value and over half of cases by number were carried out by organised gangs.

KPMG says one case involved a gang of at least 17 people living across the UK who infiltrated banks and stole cheques which they then passed to other gang members who used sophisticated technology to change the payment or payee details.

Insider fraud was also prevalent over the six months, suggesting firms still need to do more to shore up internal controls. Lower level employees accounted for more fraud than managers - £94 million across 26 cases, compared to £63 million across 20 cases by managers.

"Fraud remains extremely prevalent in the UK with professional gangs accounting for over two-thirds by value, ranging from investment stings to trading scams, card fraud and money laundering," says Patel.