How would you feel if your supermarket knew that you were getting married before you did? Or if your DNA was trawled by drugs companies that then could offer preventative treatments for illnesses likely to strike you in the future, but also share their findings with the lender debating whether to give you a mortgage?

Welcome to Big Brother Britain, version 2.0, a surveillance society where every imaginable piece of digital data – web-browsing histories, e-mails, even genetic records –is gathered and processed by organisations determined to know you better than you know yourself.

At the vanguard stands Google.

“Arguably the most powerful company in the world, they know more about you than any other group,” Whit Andrews, of Gartner, the technology analysts, says.

Even so, the world’s biggest search engine is stepping up its mission “to organise the world’s information” – all of it, apparently – by using the queries that its users tap into Google.com to build up ultra-precise portraits of them.

It wants to be the supreme life coach, offering advice on everything, from its users’ career paths to what they should do with their free time. It also wants to hit consumers with the right online advertisements, the source of its enormous wealth.

Research suggests that, so far, the public is happy to trade such intrusions for the improved services they deliver. But past bungles flag just how personal this kind of information gets.

Last year AOL, a portal part-owned by Google, accidentally released 20 million search queries. Alongside searches for Britney Spears, darker entries included: “How to tell your family you’re a victim of incest” and “how to kill your wife”.

Privacy activists may blench, but the trade in personal data is ages old, entrenched and highly lucrative.

The global market for private detectives, the top-end dominated by a circuit of former government spies, is forecast to be worth more than £100 billion this year.

On the more prosaic side of the industry sits the humble supermarket loyalty card. Tesco’s Clubcard, the country’s largest, with ten million members, will drive an estimated £400 million in extra sales for Britain’s largest grocer this year, by targeting special offers based on past behaviour.

According to Ian Brown, a senior research fellow at University College, London, who specialises in computer privacy issues, the boffins behind these schemes boast that now they can predict significant life events – a marriage, even a pregnancy – before card carriers are themselves aware.

If a shopping basket can deliver such insights, online data is an even richer seam. “People don’t realise how easily companies can build up a picture of them, based on their interactions with the web,” he says. “Services are improved, but companies are helping themselves.”

New platforms are sprouting to support a burgeoning trade in records of online behaviour.

Wunderloop, a group backed by Niklas Zennstrom, the billionaire behind Skype, recently launched the first “stock market” for logs of internet browsing habits.

It operates according to the Data Protection Act (DPA), under which consumers must give their consent for their data to change hands.

The same is not true for the legion of cybercriminals that also traffic personal information – from e-mails to credit card details – and operate in territories beyond the Act’s reach.

Elsewhere, social networking sites keep records of teenage pranks for posterity.

Genealogy sites can deliver the mother’s maiden name of anyone born in England and Wales between 1837 and 2004.

Back on the high street, Liberty, the campaign group, is concerned about the use of RFID tags, the tiny radio transmitters retailers use to keep track of stock. It says that they should be used on packaging only and be deactivated when they leave a store – presumably because they could be used to track shoppers as well as their purchases.

In consumers’ pockets and purses, credit cards are being built into mobile phones by Nokia – devices that leave an indelible trail of conversations and transactions behind them and can already be used to pinpoint a user’s location.

Cisco, Silicon Valley’s biggest company, is betting big on CCTV networks being made accessible online – part of a market that it says is worth $20 billion.

Even the jocks are getting geeky. Last year the University of Nevada’s football coach sent prospective players an e-mail resembling a web page. He monitored the links that they clicked on to help to determine their interests and how best to interview them.

However, the big bang in UK data is likely to come from government and the introduction of a national ID card – the first since Winston Churchill scrapped them in 1952. The scheme’s future is unsure (Gordon Brown is said to be less keen than Tony Blair), but the plans envisage the most detailed centralised biometric database created.

Cards could carry details such as name, gender, place and date of birth, current and previous addresses and immigration status, as well as a microchip with a digital photograph, fingerprints and iris scans.

Cards would be good news for IT groups such as CSC and Accenture, which stand to earn hundreds of millions for building the underpinning system. Critics point to exorbitant costs – an estimated £6 billion and rising – and the risk of hackers breaking in.

Others give warning of a creeping trend for data to be shared between Whitehall and the private sector. There is talk inside the Government, for instance, of the State’s data being made available to the financial sector to cut fraud.

The move would form one lane of a two-way street – security agencies already trawl the credit card transactions and phone records to track terrorists.

Amid this whirlwind of change, campaign groups such as Liberty say that the decade-old DPA has failed to keep up with the latest methods of processing data and needs an urgent upgrade.

The Information Commissioner’s Office, responsible for access to and the protection of consumers’ data, said last month that it is “regularly frustrated” by Downing Street bypassing it on key plans.

The debate will only get louder as work begins in earnest on the most personal information there is – a consumer’s genetic make-up. In an interview with The Times, Larry Ellison, the tycoon behind Oracle, the $100 billion database company, shared a vision of the future in which his company keeps track and manipulates consumers’ medical records and genetic blueprints.

Health companies given the opportunity to mine this digital information using Oracle technology will be able to pinpoint the most effective drugs for individual patients, he said.

“We are getting close to this level of personalisation,” Mr Ellison said, citing work being done in Oracle’s laboratories. “It will make society more efficient.”

Google, of course, is also interested. It has invested in 23andMe, a start-up that aims to make users’ genetic information available on the web to accelerate the discovery of tailored drugs.

Asked about the possibility of a user with a family history of cancer finding herself refused a mortgage on the basis of that data, Mr Ellison replies as if this type of sophisticated manipulation of personal information should be accepted as a basic, everyday occurence. “There is no doubt that information can be misused,” he said, “but that is true of all technologies since fire.”

In the same way that many people welcome closed-circuit television cameras because of the sense of security they can offer, internet users seem content to trade intrusions into their web-browsing histories in return for improved services. But deeply personal information can be open to abuse

Google-eyed: who's watching you?

Welcome to Big Brother Britain, version 2.0, a surveilance society where every imaginable piece of data – web-browsing histories, emails, even genetic records – is gathered and processed by organisations determined to know you better than you know yourself. At the vanguard stands Google:

— A life in Google: your details on the internet and the tools to find them

— The future: your genetic blueprint stored online

— Know your rights: How to protect your data

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