Over 500,000 names on the DNA database are false, misspelt or incorrect, the Government has admitted.
Ministers have disclosed that one in seven of the genetic profiles on the controversial database is a "replicate", raising alarming questions about the integrity and accuracy of the entire system.
Around 4 million names are on the database, which is the biggest in the world, and holds details of rapists, murderers, and suspects arrested but not charged.
Thousands asked to give their details to police upon arrest have given false names or alternative spellings of their names. In other cases, mistakes have been made in the spelling of names. Some files include names belonging to someone else, or names of people who do not exist. Altogether there are 550,000 "replica" files.
MPs have questioned whether the false data could lead to innocent people, whose names may have been maliciously given to police by suspects, being questioned about crimes they have not committed.
The revelation has led to fresh calls for an inquiry into the integrity of the system which has been dogged by controversy.
The Government admits it does not know how many files in total are inaccurate: it has only calculated those with replica DNA samples elsewhere on the system.
Lynne Featherstone, the Liberal Democrat MP for Hornsey and Wood Green, called for an urgent investigation and questioned why so much inaccurate information was on the system.
"If the database is to be of any use, then it has to be accurate. DNA data is open to abuse and this could allow people who mean no good to do no good. The more failsafe the police regard DNA, the easier it is to set someone up," she said.
New figures also show that the profiles of 150,000 children under the age of 16 are on the DNA database, many of whom have been arrested by police but found to be innocent or not charged with any crime.
The database is already the biggest in the world, but the police want to expand files on the system to include people caught dropping litter, dodging rail fares or failing to scoop up their dogs' waste.
Shami Chakrabarti, the director of the civil rights group Liberty, said the errors on the system raised questions about proposals to expand the database.
"It's bad enough that we have a DNA database stuffed with innocents not charged with any offence, containing too many children and too great a percentage of ethnic minorities. Now it turns out that we don't know the accuracy of the data.
"How many Postman Pats and Donald Ducks have entries on a system worthy of the Keystone Cops? This is hardly an advert for those who want to make the DNA database universal," she said.
Meg Hillier, a Home Office minister, admitted that because of the bogus replica files, "The number of individuals on the database is approximately 13.7 per cent less than the number of subject profiles."
A Home Office spokesman said that the police and DNA custodian unit, which oversees the database, were working hard to get rid of inaccurate files and were cross-checking fingerprints with DNA samples to ensure that the identities given by suspects were accurate.Reuse content