The accidental deletion of as many as 400,000 records from a police computer databases led to a number of “near misses” in identifying suspects in serious crimes, it has emerged.
It emerged on Friday that at least 150,000 records relating to people arrested and released without further action were scrubbed from the Police National Computer after being incorrectly flagged for removal.
But now a letter from the National Police Chiefs Council has revealed that the blunder may have affected as many as 213,000 offence records, 175,000 arrest records and 15,000 person records stored on the system which shares criminal records information across the UK.
And deputy chief constable Naveed Malik, the NPCC's lead for PNC, said: "We are aware of a couple of instances of 'near misses' for serious crimes where a biometric match to an offender was not generated as expected but the offender was identified through matches between scenes.
“However, in these circumstances, without a direct match report to the subject, it may be more challenging for police to progress to an interview or arrest."
The PNC is accessed 600 million times a year by officers for information to support local, regional and national investigations. It holds records of arrests, prosecutions, fingerprints, DNA, vehicles and other data needed for real-time checks.
Labour are calling for home secretary Priti Patel to come to the House of Commons on Monday to explain the incident to MPs.
Party leader Sir Keir Starmer said that he knew from his experience as director of public prosecutions for five years that the loss of the records was “really serious”.
“We heard that 150,000 had been deleted, we now hear that 400,000 records have been deleted,” Starmer told a Fabian Society conference in London.
“That's an increasing number, which is a huge concern, but equally of concern what we learn is that some of these now involve live cases, investigations that are going on now.
“So this isn't just a historic record, it's a record that is relevant to ongoing investigations. At a time like this, we need the home secretary to take responsibility herself for this, and at the very least, she should be in parliament on Monday, making a statement about this, explaining it, giving the full facts and facing questions.”
The mistaken deletion is understood to have started in November and been halted only last week.
The NPCC letter revealed that it was caused by a "weeding system", developed and deployed by a Home Office PNC team, erasing records wrongly.
A coding error has been blamed for records that had been flagged for deletion being lost from the database before checks had been carried out to determine whether they could be lawfully held or not.
In his letter to chief constables and police and crime commissioners, Mr Malik said that - on top of the 400,000 offence, arrest and person records - about 26,000 DNA records relating to 21,710 people had potentially been deleted in error, alongside 30,000 fingerprint records and 600 subject records.
The total information loss is likely to be lower because there will be overlaps as an individual's arrest could relate to multiple offences.
His letter said that police were already aware of at least one instance where the DNA profile from a suspect in custody did not generate a match to a crime scene as expected, "potentially impeding the investigation of the individual's involvement in the crime".
Earlier, Policing minister Kit Malthouse said the problem had been identified and the process corrected so "it cannot happen again".
He said the Home Office, National Police Chiefs' Council and other law enforcement partners were working "at pace" to recover the data.
The Home Office said no records of criminal or dangerous persons had been deleted.
An NPCC spokesperson said: “We are aware of an issue with the Police National Computer and are working closely with government to understand the potential operational impacts and resolve them at pace.”