In one case, the parents of a stillborn baby were given the ashes of what experts said were of a young adult, while their child's body was found by police in a brown paper bag.
Prosecutors said Robert Bush, who ran Legacy Independent Funeral Directors in Hull, northern England, breached the trust of grieving families "on an almost industrial scale".
Bush's deception was discovered in 2024 when, while Bush was on holiday, a casual worker told other funeral directors that bodies had been left for years, describing it as "a horror scene", prosecutor Chris Paxton said.
Police found 35 bodies on the site, with many uncovered and in varying states of decomposition having been "simply abandoned ... for nature to take its course", Paxton said.
Only the relatives of those whose bodies were found there can be sure what happened to them, Judge Nicholas Hilliard said as he sentenced Bush, whom he described as "heartless".
"The awful truth is that anyone whose loved one went through Legacy at any time when it was operating can now have no confidence as to how they were treated or as to whose ashes they have," the judge added.
VICTIMS DESCRIBE FEELING 'VIOLATED'
Bush in April admitted 30 counts of preventing a lawful and decent burial and theft, by stealing money families had donated to 12 charities, having previously pleaded guilty to more than 30 charges of fraud by false representation and fraudulent trading over nearly 12 years.
Hilliard said Bush, 48, had "caused anguish and pain on a scale beyond comprehension ... I don't think that I have ever known offences affect so many people and so many people so deeply".
During a week-long hearing at Hull Crown Court, dozens of statements were read by, or on behalf of the deceased's relatives.
One woman, whose 94-year-old father's body was left at Legacy for almost a year, said she had taken some of the ashes Bush gave her and put them in lockets for her and her mother.
"I now feel violated that I have had some unknown person's ashes so close to me," she said in her statement.
"What happened at Legacy Funeral Directors is the unthinkable, and the details have shocked the entire country," Detective Superintendent Alan Curtis from Humberside Police said.
