Police chiefs have defended the right of officers to confer in some circumstances in the aftermath of fatal shootings, such as that of Mark Duggan.

Duggan, 29, was shot in August 2011 after armed officers forced a cab in which he was travelling to stop, based on intelligence that he was part of a gang and had collected a gun.

The shooting in Tottenham, north London, triggered the worst riots in England in recent times, with several days of disorder that began in London and spread to other towns and cities.

In January this year a jury returned a verdict that the police had killed Duggan lawfully. But a report in May by the coroner Keith Cutler expressed concern that comprehensive accounts were not taken from police witnesses at the first opportunity. The officer who shot Duggan, known as V53, said that his substantive account of the shooting was written three days after the incident, when he and his colleagues spent more than eight hours together on their statements.

Andy Fairbrother, a solicitor acting on behalf of the Met, said the force accepted that the current “post-incident procedure” did not “attract public confidence and needed to be made more transparent”. It now insists that a senior officer is present while witness statements are written. But it said that, while officers are warned against conferring and there is a presumption in guidance against doing so, a blanket prohibition would not be practical. He added that police officers may be too traumatised by such incidents to provide immediate witness statements.

Duggan’s family said they were particularly distressed by a statement from the Met saying that the intended outcome of the operation against him was achieved. Duggan’s mother Pam and his brother, Shaun Hall, said that the force’s statement in response to Cutler’s report, that “the intended outcome of the planned operation – that is the interception of Mark Duggan and the recovery of the firearm from him – was achieved,” had devastated them.

“It’s atrocious,” said Hall. “Will no lessons be learned from my brother’s shooting? That comment makes us feel as if the Met don’t care about us as a family. They got the gun, but our son and brother was killed and after that we had the worst riots in modern history.”

Pam Duggan said: “Mark would have been 33 last month, had he not been shot dead by the police. The coroner has accepted his responsibility to try to prevent future deaths. But the police and other agencies are burying their heads in the sand. More mothers will be burying their children as a result. I’m ill with cancer, which I believe has been caused by all the stress of the police killing my son.”

The responses to the coroner’s concerns have now been placed on the Courts & Tribunals Judiciary website.

A police officer in the Duggan case is under investigation by the IPCC after allegedly failing to circulate intelligence about the gun which was linked to an incident in a Hackney barber shop a couple of weeks before Duggan was killed.