The government today announced plans to keep innocent people on the DNA database despite a landmark ruling by the European Court of Human Rights last year saying that they should be removed.

Those arrested but not convicted of serious violent or sexual crimes will be kept on the database for 12 years while those arrested but not convicted of all other crimes will be kept on the database for six years.

The move is a shock as the government had previously indicated the government would remove the DNA profiles, samples and fingerprints of 850,000 innocent people kept on the database.

Launching the public consultation on the proposals, Home Secretary Jacqui Smith said today:

"As I said in December, I have real sympathy for all those victims and victims' families who have concerns that any move could undermine a system that helped trap murderers and rapists, such as Sally Ann Bowman's killer."

The government also proposes to retain the profiles of anyone convicted of an offence indefinitely.

The Home Office defended the policy by saying that in 2006-7 alone there were 41,717 crimes with DNA matches, including 452 homicides, 644 rapes, 222 other sex offences and 1,872 other violent crimes.

But human rights groups and opposition politicians expressed dismay at the move and predicted a rapid legal challenge.

Shadow home secretary Chris Grayling criticised the move, saying the Conservatives favoured the Scottish system, where a DNA sample is taken on arrest but then deleted if the person is cleared.

"I can see no reason to be storing the DNA of people who have not been convicted of any offence," he said.

Director of Liberty Shami Chakrabarti said: "Wholly innocent people – including children – will have their most intimate details stockpiled for years on a database that will remain massively out of step with the rest of the world. "