'If you have nothing to hide, you have nothing to fear,' is the rationale behind the growing number of databases holding personal information on UK citizens.

But the launch of a public consultation on the ethical concerns around the government’s DNA database yesterday has sparked debate on how pervasive such information may become.

Professor Alec Jeffreys, who pioneered research into DNA profiling, and is a member of the Nuffield Council on Bioethics launching a three-month public consultation into the subject, told BBC News he feared “mission creep” in the general use of the national DNA database.

“When the DNA database was initially established, it was to database DNA from criminals so if they re-offended, they could be picked up. Now hundreds of thousands of entirely innocent people are populating that database," he said.

With 3.6 million samples the UK has the world’s biggest database of its kind, where one in five sample is Afro-Caribbean, and as many as 24,000 from under-18s who have committed no crime.

Jeffreys added the samples were "skewed socio-economically and ethnically", adding: "My view is that that is discriminatory."

And while Prime Minister Tony Blair last week said he’d have everyone on it if he could, police force representatives point out how it can help solve cold cases or identify people who do later go on to commit offences.

Similar questions are also being asked about the NHS scheme to centralise patient records as part of the £6 billion National Programme for IT, where government is said to be assuming consent for accessing sensitive data.

Clive Longbottom, senior director of IT analyst Quocirca said we should move away from conspiracy theories, but that technology should also be used to make sure checks and balances exist in how personal data is secured, accessed and used.

“The question is why would you want to opt out?” he said. “The danger is if I get ill on holiday and get given a drug I'm allergic to because of an opt-out I’d taken on some part of my medical records data. The key is to balance its security with the right number of people to access it, like paramedics, GPs, doctors and private hospitals that may treat me. It’s not having the data but what you do with the responsibility for it.”