The coroner at the inquest into the death of a five-year-old boy in an E. coli outbreak in south Wales has recommended stronger enforcement of food hygiene laws.
David Bowen said Mason Jones, from Deri near Bargoed, died in 2005 after eating infected meat.
Afterwards, Sharon Mills said she was "disappointed" an unlawful killing verdict was not returned.
About 160 people fell ill in the outbreak.
Mr Bowen, who gave a narrative verdict over the death, said: "I have agonised over a verdict of unlawful killing but despite substantial, some might say horrific, breaches of food hygiene regulations the evidence is not strong enough.
"There is little doubt Mason was owed a duty of care and a catalogue of failures to observe basic food hygiene breached that duty.
"But it is not enough for there to be a breach of the duty of care, however extensive and reprehensible that may be."
Mason became ill and died after he ate contaminated meat supplied to his and more than 40 other schools in the south Wales valleys by a butchers in Bridgend.
The coroner added: "Five-year-old Mason Jones died after being poisoned from eating contaminated meat in his school dinners.
"Mason's death was a result of an E. coli infection due to the consumption of cooked meat which had become contaminated during the course of preparation due to a lack of, or disregard, good food hygiene practices.
"One of the problems with E. coli is that there's no recognised treatment. All one can do is safeguard against the risk of dehydration.
"The strain which killed Mason was indistinguishable from the strain found in unused cooked meat supplied to schools by William Tudor."
Mr Bowen said he would be making recommendations to both the Ministry of Justice and the Welsh Assembly Government.
The two-day inquest in Newport heard that butcher William John Tudor, 58, of Cowbridge, Vale of Glamorgan, had sold rotten meat for years.
He was prosecuted for breaking food safety laws and was jailed for a year in 2007.
The inquest heard that the butcher was aware of the risks he was taking using the same equipment for cooked and uncooked meats.
Police evidence at the inquest said the same type of E. coli bacteria that had killed Mason had been found on samples of meat at the premises of John Tudor and Son in Bridgend.
The inquest heard staff had not received proper hygiene training and cleaning records were not completed.
Solicitors for Mason's family had asked the coroner to bring in a verdict of manslaughter by gross negligence.
Outside the inquest, Sharon Mills, Mason's mother, said: "My heart is broken and my life has changed considerably since this happened.
"I'm going to do whatever it takes to make sure no other family goes through what we have gone through over the last five years."
"We are extremely disappointed the coroner felt he wasn't legally able to return a verdict that Mason was unlawfully killed.
"In the eyes of our family that is exactly what happened. For that reason, we do not feel Mason has received proper justice.
"I will carry on with my campaign for as long as needs be. E.coli is never going away."