Bungling officials lost the fingerprint records or DNA profiles of 144 potential terror suspects.
Nineteen were from people who “may have posed a threat to national security”, a report by Biometrics Commissioner Prof Paul Wiles said.
They were lost from Counter Terrorism Command’s database in 2018, a year after 36 people died in attacks in London and Manchester.
MI5 rates the current threat level as severe. Prof Wiles said the blunders were “disappointing” after just 13 records were lost in 2017.
Three quarters vanished due to “an administrative error during a data transfer”, his report said.
Others were deleted because they were not reviewed within the legal time limit or were made invalid due to procedural errors by police.
The Met said it was “confident that such losses will not be repeated”.
It added: “Measures have been put in place to mitigate against the loss of the biometric records.”
