Ryanair has announced plans to cancel thousands of bookings made through internet travel sites which it claims are illegal.

The price comparison websites - known as screen-scrapers in the industry - allow customers to purchase flights without having to go direct to Ryanair, which the budget airline says runs counter to its terms of conditions and slows down its site for other customers.

"We hope that by getting rid of screen-scrapers we will speed up passenger processing times on Ryanair.com as well as ensuring that Ryanair passengers are not paying unnecessary handling charges or higher fares," spokesman Howard Millar said.

But consumer groups and travel agents have condemned the move, claiming it makes it more difficult for customers to book.

Ryanair has said it will compensate those affected by the move.