Facebook has announced it is to allow users to develop unlimited applications for use on the social networking website.

Under the move, internet advertisers will be able to create profiles, known as 'canvas pages', which will give visitors the opportunity to click-through to websites where they will be able to make an online purchase.

Chief executive and founder of Facebook Mark Zuckerberg said: "Until now, social networks have been closed platforms."

"This is going to allow any developer worldwide to build full social applications," he added.

Although any applications on such profiles will remain free of advertising, developers will be able to generate revenue through click-throughs or subsequent purchases made by users.

Amazon is reported to be one such firm getting involved with users able to click-through to the online retailer from a book or album review.

Last month, a study by Marketing Evolution revealed social networking websites such as MySpace and Facebook accounted for more than 70 per cent of marketing revenue for brands such as Electronic Arts and Adidas.