Fraud has soared by 50% across the UK to £630m in the first half of this year, with banks the worst hit.

In Scotland there has been a dramatic increase, with some 12 fraud cases coming to court in the first half of this year worth more than £22m, compared with just seven cases worth £2.7m in the same period last year.

Financial experts have warned that the problem is expected to become even more prevalent as the credit crunch unfolds.

Half of the scams were carried out by organised gangs and the financial sector was their main target with more than £350m of fraud. Government offices lost £69m.

There has been a marked increase in mortgage fraud from £3.7m in the whole of last year compared to £20m in the first six months of 2008.

In Glasgow, a nine-strong gang was arrested for mortgage fraud against a range of lenders involving properties totalling more than £3m. The investigation centres on claims that the gang were applying for mortgages using fictitious names.

Michael O'Neil, 38, and Richard Crawford, 25, from Glasgow, appeared at the city's sheriff court on fraud charges in connection with the case.

The Financial Services Authority warned of the need for the lending industry to step up its defences against mortgage fraud. While managers were responsible for some £63m in fraud such as embezzlement, the problem was more common among employees who stole £94m.

The figures were released yesterday as part of KPMG's biannual analysis of fraud cases worth £100,000 or more going to court. KPMG said the figures indicate that companies may need to improve their internal audit controls.

In Scotland, a bank worker initially fled abroad after embezzling £300,000 from her local branch from 2000 to 2005. The embezzlement involved the accused making false cheque payments into her own account. The crimes were uncovered when the bank probed a bogus £340,000 cash payment.

Ken Milliken, head of forensic for KPMG in Scotland, said: "These are worrying indicators. Fraud remains extremely prevalent in the UK and across Scotland, with professional gangs accounting for over two-thirds by value, ranging from investment stings to trading scams, card fraud and money laundering. Mortgage fraud cases have started to come through in the courts too - and it seems likely that there will be many more.

"These cases 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 12 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."

Detective Chief Superintendent Ruaraidh Nicolson, spokesman on fraud issues for the Association of Chief Police Officers in Scotland, said: "The Scottish Police Service is acutely aware of the risks associated with an economic downturn and will dynamically consider those issues as they arise."

Identity theft fears were fuelled as a man in Aberdeen was convicted of skimming almost £400,000 from more than 2500 bank accounts.

The man used a fake name, passport and international driving licence to open a bank account and have a debit-card reading terminal installed. It is alleged that he did so as part of an illegal scheme to obtain money using a streamline machine. The man acquired the details of 1235 credit and debit cards and processed the cards through the machine to have more than £345,000 credited into his accounts.