Relatives of suspects in criminal investigations are to face having DNA tests and their confidential medical records released to the authorities if they refuse to co-operate with the police.
Internal government guidelines on the use of the DNA database seen by The Independent on Sunday instruct the police to ask for medical files belonging to the relatives of criminals so their blood and tissue samples can be tested for DNA.
The secret document, prepared for police forces by the Home Office, reveal that families of suspects, and those with similar genes, are being targeted by investigators.
The guidelines show how people on the DNA database with similar genetic make-up to suspects are being approached by the police. They are then asked for the names and addresses of their relatives who will be swabbed for DNA.
Police sources said that using the DNA database to track down suspects through their families was a crucial policing tool. Around eight convictions for rapes and sexual assaults have been gained after a suspect was traced through a relative whose DNA was on the national database.
The confidential document admits there is "significant public concern" about the use of "familial searching" which involves testing people who have never come into contact with the law. It shows that people the police believe are related to criminals are being asked to give DNA samples - sometimes covertly. If they refuse, they could see their medical records released so that stored tissue samples, including blood, can be genetically tested by the police.
The guidance says officers can pretend they are doing a general DNA "sweep" when asking for swabs from people they believe are related to a suspect. And it says that people who refuse to give DNA samples should be regarded as suspicious.
Civil liberties campaigners said yesterday that obtaining medical records of relatives not suspected of committing a crime was an infringement of privacy.
Shami Chakrabati, director of Liberty, said: "Sloppy legislation and even sloppier ethics are creating a DNA free-for-all from which no one's intimate details are adequately protected. This is what happens when politicians and police decide that our rights and freedoms don't matter."
The Labour MP Ian Gibson said: "This technique is not precise. It's quite possible you could have a DNA match by accident. There is no evidence that criminal behaviour runs in families."