The UK could "sleepwalk into a surveillance society" as a result of ID cards and other plans, UK information commissioner Richard Thomas has warned.
British information watchdog says government should clarify ID cards
He told The Times he had concerns about how much information would be collected and shared under the ID card plans.
Mr Thomas also suggested he was uneasy about plans for a population register and a database of every child.
He used General Franco's Spain as an example of what can happen when a state knows too much about its citizens.
Mr Thomas says, although he is not for or against an ID card scheme itself, he is concerned about the government's failure to spell out their exact purpose.
He told The Times newspaper: "My anxiety is that we don't sleepwalk into a surveillance society where much more information is collected about people, accessible to far more people shared across many more boundaries, than British society would feel comfortable with.
"The government has changed its line over the last two or three years as to what the card is intended for.
"You have to have clarity. Is it for the fight against terrorism? Is it to promote immigration control? Is it to provide access to public benefits and services?"
A Home Office spokesman said the government remained committed to its plans for national identity cards which would, among other things, protect people against identity fraud and organised crime.
"There will be no question of a card scheme being an infringement of human rights - protection of privacy, strict limits on the information held, its use and disclosure, and ensuring independent oversight will be built into the legislation."
Mr Thomas said he did not want to sound "paranoid" but pointed to General Franco's Spain and Communist Eastern Europe as examples of what can happen when a government gets too powerful and has too much information on its citizens.
Mr Thomas also raised concerns about to the Citizen's Information Project, planned by the Office for National Statistics (ONS), which would create a population database for use by public services.
An ONS spokeswoman said a consultation on the plans was currently being held and that nothing was set in stone.
"The population register would simply act as an index to existing records held in different databases.
"These records could only be linked when specifically authorised by legislation," a consultation paper on the plans says.
ONS head Len Cook said the plans were an extension of the register of births, deaths and marriages and that he hoped it would enjoy the same level of trust from the public.
It was about tying together information on the way people relate to government, he added.
Mr Thomas also expressed concerns about a database of all children from birth to adulthood proposed in the Childrens Bill.
The proposal followed the inquiry into the death of Victoria Climbie which criticised the failure to share information about the youngster.
Under the scheme, every child would have a unique number which would enable the different organisations that come into contact with children, such as social services, police and educational bodies to share information.
Mr Thomas told the Times: "There are reasons why we need to promote better information sharing where children are at risk, but whether the answer is to create a database of every child in the country should be questioned."
A Downing Street spokeswoman told reporters Mr Thomas was making an important contribution to the government's consultations over the ID cards plans.
She stressed there would be guarantees to prevent "function creep" so information was not handed around government in an uncontrolled way.
The assistant information commissioner, Jonathan Bamford, later reiterated Mr Thomas's concerns.
He said the different databases could "flow into each other" and provide a very detailed picture of how people live their lives.
"We need to recognise that the potential's there where we build the infrastructure for a surveillance society.
"We need to make sure the proper safeguards are in place to make sure that it isn't used in a way that none of us wants. I don't think we can just leave that to chance," he told BBC Radio 4's World at One Programmme.
John Denham, chairman of the Home Affairs Select Committee which recently looked into the government's ID card plans, called for a powerful information commissioner to oversee the whole system.
A proper piece of legislation on information sharing across goverment was needed, he said, along with a "comprehensive approach".