A "substantial" number of E.coli cases could have been prevented if health chiefs had responded quickly to an outbreak at a petting farm, a damning report said today.
The Health Protection Agency (HPA) missed a key opportunity to take action which would have restricted the size of the outbreak at Godstone Farm, near Redhill, Surrey, last year.
A total of 93 people, including 76 children under the age of 10, were infected with E.coli after visiting the farm.
But the HPA and local health protection officers failed to take action which could have prevented many of these cases, according to an independent investigation.
The farm remained open over the August bank holiday weekend - receiving 5,500 visitors including 2,000 children - despite the fact officials already knew about three or four cases of the bug.
Today's report said was an "unacceptable delay" in taking steps to control the outbreak, which led to more people becoming infected and public safety being "neglected".
The study added: "The health protection unit (HPU) did not declare an outbreak, did not make any arrangements to review the circumstances over the Bank Holiday weekend, and did not convene an outbreak control team (OCT).
"No visit was made to the farm over the weekend.
"Had a decision been made on the August bank holiday weekend (or even after it, on Tuesday September 1) to stop all contact with ruminant animals, a substantial number of cases of E.coli O157 could have been prevented."
Godstone Farm eventually shut on September 12, about four weeks after the first case of the bug was reported.
Today's study, commissioned by the HPA, was led by George Griffin, professor of infectious diseases and medicine at St George's, University of London.
Prof Griffin said if the farm had been shut on the Friday, there would have been far fewer cases.
"In the week before the bank holiday several cases were spotted and brought to the attention of the local authority, these were in total three or four cases.
"At this time it would have been absolutely exceptionally good public health to have done something to protect the public - that could have been closing the farm.
"If the closure had been made by the Friday of the bank holiday, there was already 33 cases.
"As time went on there was a delay in closure and prohibition and this number increased to 93."
Symptoms of E.coli infection include diarrhoea and vomiting, and it can cause kidney failure.
It can be especially dangerous in young children because they cannot tolerate much fluid loss.
Practices at the farm were also heavily criticised in today's report, including keeping animals in pens which accumulated faeces - a major source of E.coli spread.
These pens were accessible to children, while animal seepage and runoff was able to cross visitor walkways.
Staff had no training on the risks of E.coli and the assistant farm manager - who was in charge of complying with health and safety laws - "had received no training on his health and safety responsibilities", the report said.
Some of the families affected by the outbreak are preparing to launch a group legal action.
Twenty-seven people were admitted to hospital after the outbreak, with two kidney dialysis units in London filled with children affected by the bug.
Today's report criticised "a lack of leadership and a paralysis of decision-making" by those in charge of controlling outbreaks.
An outbreak control team under-estimated the scale of the risk and the number of cases linked to the farm, it said.
Prof Griffin added: "This outbreak could very likely have been avoided if more attention had been given to visitors being exposed to animal faecal matter.
"Once it had started, there is no doubt that, even with prompt action, this would have been a big outbreak.
"Nevertheless there was a lack of public health leadership by the Health Protection Agency and a missed opportunity to exercise decisive public health action and thereby restrict the size of the outbreak.
"The assessment of risk carried out by Godstone Farm was inadequate and it principally relied on the actions of the public, primarily through hand-washing, to control the risks."
Godstone Farm is the biggest ever E.coli outbreak in the UK linked to animals.
People can become infected with E.coli in several ways, including through consuming contaminated food or drink.
They can also get E.coli through direct contact with contaminated animals, or by contact with an environment contaminated with animal faeces.
Direct spread from person to person also occurs, particularly in families and between children.
Today's report said more attention needed to be paid to the risk of E.coli at all open farms across the country.
It said the Health and Safety Executive and local authorities "continue to regard the risk of infection to visitors at open farms as low" but this level of risk is "not acceptable".
It added: "We conclude that the outbreak at Godstone Farm was not exceptional, other than in terms of its size.
"We believe that, unless the factors described are addressed, other large outbreaks at open farms could occur in future."
Justin McCracken, chief executive of the HPA, said the organisation would act immediately upon all the recommendations.
He said: "The report makes clear that many factors contributed to this incident, including the fact that the HPA should have acted more quickly in this instance.
"The HPA responds effectively to thousands of such outbreaks and incidents each year but of course is very sorry for its part in what happened at Godstone.
"That is why I publicly apologised to parents at the time.
"I am determined that the HPA will work with the other bodies to prevent a similar situation developing in future."
Jill Greenfield, a partner at law firm Field Fisher Waterhouse, who is representing at least 25 children and one adult, said: "From the evidence in the report, it does appear that at every possible level there were fundamental failings in the handling of the outbreak. Such failings are simply unacceptable.
"Many of the children that I am representing suffered significant pain and distress and continued to require medical treatment.
"We will not know for many years whether or not they will require further dialysis and/or kidney transplants."
Among those affected were Tracy Mock's three-year-old twins, who spent weeks in hospital fighting the bug following a visit to the farm.
Her son, Aaron Furnell, suffered acute kidney failure and has to be taken to the Evelina Children's Hospital in London every six weeks for blood and urine tests. He still uses a feeding tube for ingesting liquids.
His twin Todd, who has 80% kidney function, is due to have a further check-up in September and more tests next year.
Paul Bettison, chairman of local government body the Local Authorities Co-ordinators of Regulatory Services (Lacors), said farm regulation must not become "too excessive".
He said those affected "deserve our sympathy" but added: "The important thing now is to establish the right middle ground between safety and enjoyment for millions of children."