Google says that its cookies, which store information about a user's internet habits on their own computer, will now automatically be deleted after two years.

The move comes after a group of European data protection watchdogs wrote to Google questioning the legitimacy of its privacy policies last month.

'After listening to feedback from our users and from privacy advocates, we've concluded that it would be a good thing for privacy to significantly shorten the lifetime of our cookies,' said Peter Fleischer, Google's global privacy counsel.

But the cookies will only auto-delete if the user does not visit a Google site in that time. If they do, the two-year clock is reset, leading to criticism of the move by many as a token gesture to privacy.

Google says that all users can delete cookies from their web browser manually at any time, and that there are tools online which can prevent cookies being left on a computer.

In March, the search giant said it would anonymise personal data received from users' web searches after 18 months.