eBay warns buyers to beware of the 'second-chance sellers'

The starting point for the scam is that eBay users can see which fellow bidders are participating in auctions. It is then possible to contact unsuccessful bidders through eBay's "contact a user" service.

In many cases, unsuccessful bidders have received e-mails from sellers claiming that their sale to the auction winner has fallen through. The e-mails seem authentic, because they are delivered through eBay's own systems, which were set up to enable users to do legitimate business with each other.

Bidders are then asked whether they would like to buy the item outside the eBay system. After they part with cash, the goods are never delivered and the seller disappears.

eBay said the auction site was aware of a number of cases of attempted second-chance fraud. The scam has already caught out thousands of users of eBay's US site, and the fraud was imported to the UK last year.

"An offer to sell an item directly to another eBay member through e-mail violated eBay rules, and it is clear in our marketplace safety tips that anyone who receives such an e-mail should report it," a spokesman said.

"We strongly discourage anyone from taking a transaction off eBay as you are no longer protected by eBay safety measures such as our standard purchase protection programme."

The auction site is particularly concerned that second-chance fraudsters are attempting to persuade people to use instant money transfer services such as Western Union, where there is no way to seek redress if a transaction goes wrong. eBay's own payment service, PayPal, offers guarantees about security, as well as a compensation scheme.

eBay has repeatedly been targeted by fraudsters. In particular, it has become one of the leading targets for the "phishing" scams usually aimed at bank customers. Users receive e-mails purporting to be from the site, urging them to update their credit card details – but customers who disclose such information are robbed.