SELLING unwanted Christmas gifts or old items you no longer need is easier than ever with services such as eBay – but beware of crooks out to dupe you.

Fraud experts have warned of an increase in cases where bogus buyers lie about having paid for or received items — leaving sellers out of pocket.

The crooks send a fake proof of payment such as a doctored bank transfer receipt and then pressure the seller into sending over the item.

Or they simply lie and pretend it never arrived or was faulty to get a refund.

James Kilpatrick was caught out after he used Facebook Marketplace to sell his old Hawx 120 ski boots which he had originally bought for £300.

The 35-year-old start-up worker, from Dalston, East London, says: “I’d never used Marketplace before but I thought I’d put some things on there and sell locally.

“When someone contacted me from Worcester about the ski boots I was, at first, quite hesitant because I couldn’t be bothered to post them.

"However, I decided to do it as there were no local requests.

“The seller sent me a screenshot of a bank transfer receipt from a Halifax account which made it look like he’d paid me £80.

"I’m guessing it was doctored.

“I should have gone into my bank account to check the money was there — but, to be honest, I didn’t question it.

“I sent the boots off and when I checked the account, there was nothing there.

“I went to send a message to them on Facebook but they had disappeared.

"That’s when I’d realised I’d been done.”

Complaints-handling website Resolver has warned of widespread problems with buyers fraudulently claiming they either haven’t received goods or they are faulty.

The problem is so great that tech firms have developed anti-fraud payment methods.

Money is held in a third-party account and only released when both the buyer and seller are happy.

Tom Clementson, of digital payment protector Shieldpay, warns: “Sellers beware — buyer fraud is on the rise.

“Online scammers have become increasingly sophisticated in recent years and the problem extends to a whole new breed of fraudulent consumers whose false claims are causing a huge headache for online marketplaces.

“All too often the seller foots the costs, with little or no consequences for the fraudulent buyer.”