MPs last night blamed "appalling" blunders by police and spies for the loss of potentially vital forensic evidence.
They reportedly failed to complete major paperwork – meaning the biometric data could only be held for six months.
The revelation comes at a time when Britain is on a high terror alert following Islamic State attacks in France and Belgium.
Fingerprints and DNA profiles of 810 suspects had to be destroyed, according to the UK's biometrics commissioner.
Alastair MacGregor QC said the the "great majority" had been swabbed as part of a terrorism probe – but did not give an exact number.
Speaking to the Telegraph, he blamed the destruction of the evidence on "repeated delays" in transferring DNA material by police.
Keith Vaz, the chairman of the Home Affairs Committee, said the news "does little for public confidence".
He said: "There needs to be an urgent investigation to get to the root of this problem."
And Tory MP Tim Loughton said: "It is quite appalling that the police fail on a technicality to keep [the suspects’] details."
Asst Chief Constable Alan Barr said a "number of different factors" were responsible for the biometric data being deleted.
He said: "We have worked with the biometrics commissioner to develop a comprehensive plan to rectify the immediate issues.
"The risks these individuals potentially pose are being managed in conjunction with partner agencies to minimise any long-term risk to the public."