The new rules require websites and advertisers to obtain a user’s permission before placing cookies – small text files that allow a site to recognise an individual user and provide tailored content or advertising – on their computer.

Each member state of the EU must decide for itself how to incorporate the regulation into its national law and how to enforce it.

The UK government says it will be talking to browser manufacturers to see whether settings can be changed to make sure that users have a clear choice about whether or not to accept cookies from sites they visit. The new rules are supposed to come into effect on 26 May, but the government said they will not be enforced until organisations have had a chance to put solutions in place.

Communications minister Ed Vaizey said: “We recognise that work on the technical solutions for cookie use will not be complete by the implementation deadline. It will take time for meaningful solutions to be developed, evaluated and rolled out. Therefore we do not expect the ICO [Information Commissioner’s Office] to take enforcement action in the short term against businesses and organisations that work out how to address thier use of cookies.”

Vaizey said the new rules would bring regulation up to date and create a “level playing field” across Europe.

Publishers and advertisers have argued that they need to use cookies to provide functionality, tailored content and ad-supported services online. But regulators are concerned that web users don’t have a good enough understanding of how cookies are being used to track their activity, or sufficient control over when and how they are deployed.

Yesterday online advertising body IAB Europe launched a self-regulatory framework, including guidelines for targeted advertising, and a website where internet users can opt out of being tracked by particular companies for advertising purposes.

The European Union’s online security agency has said their should be a review once member countries have incorporated the directive into their national laws, to make sure that the practical measures taken give users a real choice about how cookies are used.

Editor’s note, 9/5/11
This story originally said that the new rules were “to come into effect” in the UK on 25 May. In fact they must be incorporated into UK law by 25 May, and will come into effect on 26 May. This has been amended above.