One of the knives purchased by Watchdog
EBay has said it intends to ban trade in all knives, apart from cutlery knives, on its UK and Ireland websites.
The ban will be implemented "as soon as possible" in order to provide a "safe" marketplace for its members, it said.
EBay said the ban was the best measure, bearing in mind the "complex" laws surrounding knife sales in the UK.
The move comes after BBC Watchdog researchers revealed they had been able to buy knives illegal in the UK through the public auction site.
All six knives purchased by Watchdog were sold by US sellers through eBay's site in the UK.
One of the knives was intercepted by Customs officials.
"The security measures we already have in place are designed to make sure that only legal knives have been offered for sale by UK and Irish sellers on our UK and Ireland sites and we are satisfied with how these measures have been working in both the UK and Ireland," said Mark Lewis, country manager for eBay UK.
"However, the laws surrounding the sales of knives are extremely complex and so we have decided that the best way to protect our members and achieve the safety guarantees they have come to expect from us is to remove and ban all knives, with the exception of cutlery knives, from our UK and Ireland sites," he added.
A company spokeswoman confirmed eBay would attempt to implement the ban with urgency, but said that due to the marketplace nature of eBay and the need to give due notice to users, it would take some time.
The company already has measures in place to try to prevent the sale of illegal knives and the purchase of knives by under-18s.
These measures include filters, and buyers must insert a credit card number because Debit, Solo and Electron cards - which some under 18s have access to - are not accepted.