Jessica Ogden said she had notified both eBay and the Metropolitan Police that her stolen clothes were being openly sold, but neither took action.
Ogden has subsequently contacted all 16 people who had bought the hand-knitted items, telling them they were stolen. Only one replied, saying they did not support such activities, but made no attempt to return the garment.
The designer said that she was "heart-broken" to see the items being sold, adding: "It was ridiculous to watch people buying my clothes on eBay. I felt very bad about it because I don't have some kind of production line - these are hand knitted for me and each one takes about two days to produce. It is a lot of time and effort for both myself and the knitters."
She said she was angry that she had heard nothing from the police for almost a month until she went to the media about her plight.
A spokesman for Scotland Yard said that although the matter had been reported to police, it had not been referred for further investigation at the time. He added: "It is now being further investigated. We cannot explain why it was not investigated at the time."
The clothes were in a consignment of two boxes being delivered to Selfridges by the courier company TNT during the summer from Ogden's studio in Kentish Town in north London. When it was realised that one of the boxes had failed to arrive, Ogden asked the courier company to investigate. She was still waiting to hear from them when she was alerted by a friend that items of hers were being sold on eBay. "I realised that this wasn't just somebody who had legitimately bought one of my items and didn't want it. This was brand new."
She notified both her local police, by telephone, and eBay, by e-mail. Although she received an automated acknowledgement from the auction house, it was three days before the police called her back with the crime number to register the fact that the report had been logged.
Over the next few weeks, Ogden logged on to eBay regularly to see her items being auctioned in batches. Among them was a cashmere cardigan, which would normally retail for £360 being sold for £31, while a merino wool gilet, normally £270, was sold for £43. Some of the buyers commented on the quality of their purchases and the fact that they were as new. She bought one item herself, a silk scarf, which is normally sold for £160, and her bid for £37 was accepted. "I stopped the auction, but I haven't paid any money over. The seller is waiting for me to pay," she said. Only two of the stolen items have not been put up for sale. "But the seller is still online, selling other clothes," she added.
Ogden is recognised as one of Britain's most innovative designers and regularly shows at London Fashion Week.
eBay warns customers on its site that any suspicions about stolen items must be reported first to police and that action to bar sellers will only be taken if the site is contacted by police. A spokesman stressed that the company always worked closely with police and that the open nature of the site made it hard for stolen goods to be sold.
Ogden said yesterday that the site had now contacted her to apologise for its delay in responding. But the success of the auction site, which is said to have up to 10 million UK users, has been accompanied by persistent reports that it has replaced the pub and the car boot sale as a means of selling goods obtained illegally.