Civil liberties campaigners have expressed concerns over a senior policeman's idea that taking DNA from babies could help solve crimes.
Figures show 5% of people in the UK are on the DNA database
Commander Dave Johnston, giving a personal point of view, said that samples could also be taken from people renewing passports and from migrants.
However, human rights group Liberty has warned of turning Britain into a "nation of suspects".
The UK's DNA database currently has just over 3.6 million samples in it.
Commander Johnston said that he thought extending the amount of DNA being held would also help prevent crime.
The head of the Met's Homicide and Serious Crime Unit also suggested taking DNA from dead people might help "cleanse" the database.
He added that blood samples were already taken from babies at four days old to test for genetic diseases but stressed it was important to have a debate over the human rights issue.
However Liberty Legal Officer Anna Fairclough said: "A proposal like this begs the question - do we really want to turn a nation of citizens into a nation of suspects?
"A better alternative would be to create a smaller, more manageable DNA database of those convicted of sexual and violent offences which will be of less cost to our privacy and our pockets."
Critics have also claimed that most crimes do not leave a DNA trace and they fear that the information could be abused.
DNA samples are retained from those arrested but not convicted and from victims and witnesses who give their consent.