The growing popularity of online banking and shopping has created fertile new ground for organised crime and Eastern European gangs are muscling in on a market that was once the province of independent hackers, virus distributors and e-mail spammers.

Banks could now refuse to honour the debts of internet fraud victims after a surge in attacks against online accounts, The Times reported at the weekend.

In the United States alone, online identity-theft scams known as phishing have victimised hundreds of thousands of people and cost their banks and credit-card issuers more than $1 billion in compensation.

Clearswift’s November Spam Index,the most in-depth spam analysis to date by an e-mail security provider, investigated more than 19,000 spam e-mails.

The survey reveals the increasingly sophisticated techniques deployed by criminals to gain control of internet users’ computers, credit card details and cash.

With Christmas now less than six weeks away a significant proportion of scams are pegged to seasonal gift suggestions and bogus order confirmations from well-known online retailers such as Amazon.

“There is a good chance that the level of internet fraud could be higher this Christmas than ever before,” said Alyn Hockey, Clearswift’s technical director.

Despite concerns over the security of some internet transactions, busy British consumers are becoming more comfortable with online shopping as an alternative to braving the Christmas crush in “bricks and mortar” shopping centres, he said.

“Already 5 to 10 per cent of all spam e-mails are Christmas-themed. If you get an e-mail that’s about Viagra or something porn-related then obviously a lot of people won’t open it but if it poses as an innocent order confirmation they are more likely to be taken in.”

There are three main scams in circulation at the moment.

The sender could be offering cheap gift suggestions, such as remote-controlled cars, which turn out not to exist. “Most consumers don’t bother to complain. They just write the cost off and put it down to experience,” Mr Hockey said.

“Others are trying to persuade shoppers to open an attachment that will install software on to their computer that will help the spammers get access to private information like passwords and credit card details. This is about stealing information.

“The third group are opening up access to private computers so they can be used at a later date to distribute viruses or more spam.”

Access to these computers can then be sold on to criminal organisations to help to launder money looted from victims of phishing scams. The technology analysis firm Gartner predicted last week that social engineering — the manipulation of people rather than machines to breach security — would be the biggest internet security threat over the next ten years.

British banks are working closely with the National Hi-Tech Crime Unit and the Association of Payment Clearance Services to educate internet users about the dangers posed by internet crime. “We take this type of fraud incredibly seriously,” a spokesperson for Barclays Bank said. “We are doing a lot of stuff behind the scenes but we don’t want to alert the fraudsters to what it is.”

The crime unit is currently focussing its efforts on investigating phishing and trying to establish the indentify of the individuals behind it, which includes organised crime figures.

A spokeswoman said: “Specifically, we are targeting the mules, the people who are helping to launder the money out of the country. These people are found by phishers through e-mails, job recruitment channels and internet chat rooms to receive money into their accounts and wire it out of country.

“Some of these people are not aware of what they are doing and don’t realise that it is money laundering.”

She added: “I would remind people that because Christmas is a time where everyone is spending more money there is more opportunity to steal that money. People need to make sure that they are on a registered site and that they are looking out for scams.”

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