Serial rapist was reported eight times to police but no action was reportedly taken until his arrest in 2021

All of those facing action were from the Met’s anti-corruption unit, according to the IOPC. Photograph: Kirsty O’Connor/PA

Four police officers and a civilian employee are to face disciplinary action for alleged errors that helped leave the serial rapist David Carrick free to attack a string of women.

Carrick, who served in the Metropolitan police, was reported eight times to police over a series of allegations, but no action was taken until his arrest in 2021.

The Independent Office for Police Conduct said all those facing action were from the Met’s anti-corruption unit, the directorate of professional standards.

One detective sergeant faces allegations of gross misconduct, which if proved, are sufficiently serious for them to be sacked and barred from any job in policing.

The IOPC said this incident related to rape and sexual assault allegations about Carrick received in February 2021, which at first police dropped.

The Guardian understands Carrick was later convicted of this attack, and that IOPC investigators believe that the Met investigation into potential discipline offences did not speak to the female complainant.

Carrick was reported first to Sussex police, who passed the criminal case on to Hertfordshire police. It dropped the criminal case, but informed Carrick’s employer, the Met.

The Met then dropped its discipline investigation into Carrick. The IOPC said: “We found that a detective sergeant should face a gross misconduct hearing for potential breaches of the police standards of professional behaviour relating to their alleged failure to supervise adequately that Carrick conduct investigation. We also found that a detective constable and a police staff member should face misconduct meetings.”

The IOPC found two other sets of discipline allegations against Carrick may have been mishandled.

In 2016 a former partner made criminal allegations of harassment and assault to Hampshire police, but no criminal case was brought. The Met’s DPS was informed and no discipline action was taken against Carrick. The IOPC says two officers should face misconduct proceedings “for failing to adequately investigate potential misconduct”.

Both were serving with the Met at the time, though one is now with City of London police.

In 2019 another former partner complained about Carrick to Hertfordshire police and no criminal action followed. The Met did not bring disciplinary action against Carrick.

The IOPC has decided that two chief inspectors “should be subject to the reflective practice … relating to their failures to investigate the allegations as potential misconduct.”

The IOPC also said a 2002 case would have led to a misconduct hearing but two officers who at the time were inspectors in the Met, had now retired. That case involved a claim of assault and harassment against Carrick by a former partner. The IOPC said: “Carrick was spoken to by his line manager but no referral was made to the directorate of professional standards (DPS).”

Carrick was finally arrested in October 2021, with the publicity then leading to other women coming forward.

In 2023 he pleaded guilty to 85 serious offences against 12 women, including 48 rapes.

Despite the allegations against Carrick the Met gave him a gun and entrusted him to guard parliament and diplomatic sites after missing clue after clue about the danger he posed.

He had served in the same unit as Wayne Couzens, who was convicted of the kidnap and murder of Sarah Everard, and the publicity about Couzens’ conviction led a woman to come forward in October 2021 that led to Carrick’s arrest.

His campaign of terror against women started in 2003, two years after he joined the Met, and lasted 17 years, with Carrick seemingly emboldened by the failure to take any action against him.

Mel Palmer, a regional director at the IOPC, said: “In all cases we identified that officers failed to properly explore, investigate or oversee the misconduct investigations against Carrick, who never faced any disciplinary proceedings despite being the subject of serious criminal allegations on multiple occasions.

“Had these matters been progressed appropriately, Carrick may have potentially faced gross misconduct proceedings and been dismissed from the force well before he was eventually arrested.”

In June two officers from the Wiltshire force were disciplined for misconduct after the bungling of an investigation into Carrick after claims he had abused a woman. In that case the Met were not informed.

The dates for the hearings are still to be arranged.