Couzens has been issued a whole-life sentence for the murder of Sarah Everard. Following his arrest, Couzens’ phone was seized, with a group chat allegedly including constables from three forces.
The chat is claimed to have seen Couzens swap alleged misogynistic and racist messages with other officers.
The Met Police is alleged to have left two officers on duty while they are under investigation.
Other forces are believed to have suspended their officers, who faced less serious allegations, and remove them from their workplaces during the investigation.
The Met said its officers, who are under investigation, had been placed on restricted duties.
Two constables and a former officer with the Met are under criminal investigation by the Independent Office for Police Conduct (IOPC) over the message group.
Another Met officer is under investigation for potential disciplinary and gross misconduct offences, as well as an officer with the Norfolk force and one with the Civil Nuclear constabulary.
Couzens served with the three until he transferred to the Met in 2018.
Messages on the WhatsApp group involving police officers included alleged offensive and abusive terms about women.
Messages recovered so far by investigators began in March 2019, two years before Couzens murdered Sarah Everard.
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Sue Fish, a former chief constable of Nottinghamshire, said it was “beggars belief” the Met have kept the officers on duty
She said to the Guardian: “It sends the most appalling message. That clearly demonstrates the Met does not get it … does not get the seriousness.”
Brian Paddick, a former Met deputy assistant commissioner, said his former force risked appearing not to take the issues seriously enough.
He also told the outlet: “If I were still in the Met, I would be looking for every opportunity to reassure women in particular that we take this very seriously, and that does not appear to be the message the Met is sending at the moment.”
The IOPC also issued a statement to the outlet about its investigation.
They said: “They are being investigated for gross misconduct for allegedly sending messages of a discriminatory and/or inappropriate nature, and for allegedly failing to challenge the messages sent by the others.
“Two of the MPS [Met] officers and the former MPS officer have also been notified that they are being criminally investigated for improper use of the public electronic communications network under section 127 of the Communications Act.”