Three of Harold Shipman's victims could have been saved if police had investigated properly, the inquiry into Britain's worst serial killer has said.
Shipman killed at least 215 of his patients in Hyde and Todmorden
The two Greater Manchester Police detectives who investigated the doctor were inexperienced and unfit to handle the case, the inquiry found.
As a result they missed many opportunities to bring Shipman's crimes to light.
"If the police and the coroner had moved with reasonable expedition, the lives of Shipman's last three victims would probably have been saved," said Dame Janet Smith, the judge heading the inquiry.
She also called for "radical reform" of the way coroners work in England and Wales, after Shipman managed to evade their scrutiny by saying his victims had died of natural causes.
Greater Manchester Police apologised to the families of Winifred Mellor, Joan
Melia and Kathleen Grundy whose lives the judge said could have been saved.
Dame Janet's findings were welcomed by victims' relatives as "thorough" and "long overdue".
The initial police inquiry was triggered when another GP raised concerns Shipman might have been killing his patients.
Two officers "found no cause for concern" and ended their inquiry after three weeks.
The senior officer, Chief Superintendent David Sykes, was "unable to give effective leadership" but did not do anything about it, Dame Janet said.
And the junior officer, Detective Inspector David Smith, was "out of his depth" and made "many mistakes" but did not ask for help and later lied to cover them up, she said.
In particular, Mr Smith missed the chance to order post-mortems on two suspected victims which would have led to a full investigation, she said.
An internal policy inquiry after Shipman's trial into the two officers' investigation was also "quite inadequate", she said.
Only once the Shipman Inquiry began did the force carry out a thorough internal inquiry into Mr Smith's investigation and finally admit it had been "seriously flawed".
Kathleen Grundy was one of the victims that could have been saved
Relatives said the inquiry would go some way to preventing such systematic murder happening again.
"The police made terrible misjudgements and today it's been brought into the public arena," said Barry Swann, whose mother Bessie was killed by Shipman in 1997.
"It could happen again, but as long as these recommendations are taken on board it will go a long way to stop it."
Suzanne Brock, whose grandmother Edith was killed by Shipman in 1995, said she was "extremely pleased" at the thoroughness of the investigation.
Both said they would await Dame Janet's final report before deciding whether to take action against police or anyone else.
Changes to police practice had already been made, said Greater Manchester Police's Assistant Chief Constable Dave Whatton.
"The basic problem was that the wrong people were in charge... this sort of thing will not happen again," he said.
Mr Smith was already under investigation for misconduct over this inquiry, he added.
Home Secretary David Blunkett said he took the criticisms of the police "extremely seriously" and was awaiting a full report by the force.
Home office officials were working with the police to improve the investigation of alleged wrongdoing by health professionals, he said.
At least 215, possibly many more
Shipman convicted of murdering 15
Oldest victim - Ann Cooper, 93, of Hyde, Greater Manchester
Youngest victim - Peter Lewis, 41, of Briardene, Denton
Mr Blunkett said other recommendations, including changes to coroners' practices, death registration and cremation certification processes, were already being studied.
Shipman, 57, was jailed for life in January 2000 at Preston Crown Court for murdering 15 of his patients.
The deaths of hundreds more were investigated at the public inquiry at Manchester Town Hall, which found he had killed at least 215 people and probably more.
His oldest victim was 93, his youngest 41. He killed over a period of more than 20 years until 1998, mostly with injections of morphine.
The inquiry's final reports, on controlled drugs, and disciplinary systems and complaints, are expected next year.