Google has cut the lifespan of the cookies software it uploads to millions of users' computers to keep track of their online habits in an attempt to assuage mounting privacy concerns.

The internet search and advertising group will begin "in the coming month" to issue cookies that expire two years after a user visits its website — but will be updated each time they come back.

At present Google’s cookies last until 2038.

Privacy experts welcomed Google’s willingness to revisit a controversial policy, but said that the move would have little impact on how the company’s “cookie monster” operates and the amount of information the company stores on users.

Cookies are small data files that are automatically downloaded to users' computers when they visit search engines and most other websites.

They are used to gather and transmit information on a users’ preferences by “remembering” aspects of previous visits.

Google, for instance, says that it uses a "PREF cookie" to remember its users’ basic preferences — the language a user wants to receive search results in, for example, and whether they have chosen options such as a SafeSearch setting to filter out explicit content.

Cookies play a key part in making websites work smoothly and are used by every search engine. Google’s, however, have been a consistent target for critics of the company’s privacy stance and in recent months the group’s privacy policies have come under greater scrutiny.

The Article 29 working group — made up of national European Union data watchdogs, including the UK’s Information Commissioner’s Office — wrote to Google in May asking the company to justify keeping logs of internet searches that can be used to identify individual users for two years.

Google responded by cutting the length of time it stores that information to 18 months.

Meanwhile, competitors including WPP, the advertising group, and Microsoft, the software giant, have complained that Google's $3.1 billion acquisition of DoubleClick, the largest broker of online banner advertising, will make it privy to a vast amount of data on consumer habits and companies' web-marketing spending.

That deal is the being investigated by the US Federal Trade Commission, the competition watchdog.

Times Recommends

• Lies and cover-up at MG Rover exposed by report
• High oil prices push manufacturing costs up
• Primark founder steps down as chief executive