Mr Clarke wants an expanded national DNA database

John Clarke said a national DNA database would have "a massive impact on crime".

Prime Minister Tony Blair has said he wants as many people as possible on a DNA database.

Mr Clarke said abuse of the system - from selling or manipulation of DNA information - was possible but he was confident problems could be resolved.

"If you are a law abiding citizen then you would have nothing to fear from this database," he said.

"The safeguards have to be put in place and the human rights issues considered - but people want us to catch criminals and do our best and this is one of the tools.

There is always a risk that the information might be used unwisely Anna Fairclough, Liberty

Anna Fairclough, legal officer for human rights organisation Liberty, said: "Most crimes have nothing to do with DNA and most criminals are already on the database we have got."

She said despite the massive increase in the database in the past few years, the rate of crimes solved using DNA has not increased and has remained at about 0.5%.

Although DNA is a useful crime-solving tool, it is different to say the entire nation is a suspect and an entire national DNA register is needed, she said.

"There is always a risk that the information might be used unwisely", she said.

The UK DNA database currently contains just over 3.6 million samples - 5% of the country's population - while the figure for Austria is 1%.

As well as criminals, samples are retained from those arrested but not convicted, and from victims and witnesses who give their consent.