Millions of innocent people who have reported a crime have their details stored on police databases, a Freedom of Information request has revealed.
The Press Association study found forces in England and Wales have kept data on people who called them.
Senior officers said gathering data was necessary to fight crime, protect the vulnerable and ensure concerns were dealt with properly.
But privacy campaigners including Big Brother Watch expressed their concerns.
Evidence of the police databases was collected in a series of FOI requests.
A total of 13 forces responded with details revealing how they held between 10,091 records - in Lincolnshire - and 1.1 million records, which West Midlands Police had amassed over the past 12 years.
The majority of forces said it was not possible to collect the information because the scale of the task was too big.
Others, including Lancashire, Cleveland, Avon and Somerset, Gloucestershire, West Mercia and North Wales, hold more than 150,000 each.
Hertfordshire Police said it held 1.6 million records of all kinds generated since 1989, while Sussex said it held 5.6 million records gathered over seven years.
These records included details of millions of victims of crime as well as suspects and offenders.
Police forces said personal information was spread across up to 22 databases and warned details of the same person could be recorded several times.
They said staff and officers were following guidance published by the National Policing Improvement Agency (NPIA).
In some cases, police staff not only record names, addresses and contact details, but also the caller's date of birth and ethnicity.
Gus Hosein, of Privacy International, said there was a point at which the police "stopped seeing members of the public as the people to be protected and rather see them all as potential criminals".
"Until now, this only happened in non-democratic states, but I fear that this line has been crossed in ours.
"This only goes to show how far the last government went in promoting this view that we are all criminals, and my understanding is that while this government has cut the NPIA, which is a first step, a culture change in the way we are governed and protected is the next one," he said.
Daniel Hamilton, of Big Brother Watch, said: "For the police to log this kind of information isn't just wrong - it's dangerous.
"The public must be confident that, when they report a crime, they do so in the comfort of anonymity and without risk of their details being stored on a central police database which can be accessed by thousands of people.
"This information must be deleted before public confidence in the police takes yet another hit."
Guy Herbert, of campaign group NO2ID, said police should only use the information to pursue the original inquiry and for investigations and not share it with others.
He said: "Just being on a database does not necessarily make it 'Big Brother'. It is how the information is used that is important."
Ian Readhead, director of information at the Association of Chief Police Officers, said forces should only record information relevant to the call.
The retired Hampshire deputy chief constable admitted an "amicable exchange of information" could be used against callers in the future but said most people would expect police to hold on to it.
"What is important is that data is retained in applications that are clearly transparent and subject to audit and that the Information Commissioner is content with the business processes.
"We must be transparent and reassure the public that the information is not being misused. The volume of information held by the police service can be vast and one of the things we must do is ensure compliance," he said.