The Metropolitan police have rejected claims that the force put children and vulnerable adults in danger by reportedly relaxing its vetting system for thousands of people.

Up to 20,000 members of the public have been issued with disclosure and barring service (DBS) certificates without full security checks after senior Scotland Yard officers decided to relax the process in 2016 amid criticism over delays, according to leaked documents.

The Met temporarily dropped checks on police intelligence databases and opted to solely use information on the police national computer system, which only contains records about reprimands, warnings, criminal convictions and cautions, according to documents seen by the Sunday Times.

At the time, the force was heavily criticised by the government for delays in background checks, which meant thousands of would-be NHS workers, carers and teachers could not work.

The use of police intelligence in background checks was mandated under the DBS system following the murders of the 10-year-old schoolfriends Holly Wells and Jessica Chapman in 2002, who were killed by Ian Huntley, a caretaker at a secondary school in Soham, Cambridgeshire.

Huntley had no convictions for sexual offences before he was appointed, but had previously been reported to police on six occasions over sexual assaults or sexual relationships with underage girls. Police checks failed to unearth his past, prompting reforms in the national vetting system for people working with children and vulnerable adults.

The Met confirmed that some cases were closed based on a risk assessment under “very strict guidelines”, but denied that the force’s decision to reportedly relax its background check system had put the vulnerable at risk.

Scotland Yard said: “The Met rejects the suggestion that cases were improperly closed placing the most vulnerable in danger. Safeguarding is, and will always be, of paramount importance to the Met.

“In June 2016, the Met confirmed that there were over 81,000 outstanding cases with an average waiting time of 59 days. This presented risk to the most vulnerable, in that employment of key workers could be significantly delayed.

“Alternatively, an unsuitable employee could take up employment before local police checks were completed. The cause of the problem was acknowledged as a significant increase in demand for the Met disclosure service, as well as the recruitment and retention of staff.”

The Met added that a sample of the closed cases had been reassessed and found that police intelligence would not have been used in these cases.