Campaigners have had to shelve plans for legal action over the controversial measles, mumps and rubella vaccine.
MMR jab is highly controversial
The High Court was due to hear the cases of more than 1,000 children who developed medical problems their parents believe were linked to the jab.
But the campaigners were unable to overturn a decision to deny them legal aid.
Most scientists believe the vaccine is safe despite fears of a link to autism and bowel disorders.
Several high profile studies have found the vaccine to be safe, and no research has been produced prove that the vaccine poses a genuine threat to health.
Supporters of the vaccine are angry that negative publicity has led to a signficant drop in the numbers of children receiving it, arguing that low immunisation rates increase the risk of a measles epidemic.
An independent funding review committee upheld a decision taken by the Legal Services Commission (LSC) that in the absence of any scientific proof that the vaccine was dangerous, the legal action - against the drug companies who manufacture the vaccine - stood little chance of success.
The LSC said it would be wrong to spend £10m of public money pursuing the cases.
The children involved in the court cases suffered disabilities such as autism,
bowel problems, epilepsy and other learning difficulties.
JABS, which supports parents of vaccine-damaged children, described the decision to deny legal aid was "illogical, perverse and not in the public interest".
National co-ordinator Jackie Fletcher said: "The decision to halt the cases
now, following the provision of new evidence in support of the children's cases, will only confirm the view that the combined powers of government and drug companies are working against vaccine victims receiving justice."
Ms Fletcher's 11-year-old son had the MMR jab and developed epilepsy and other problems afterwards. She believes that the triple vaccine caused the health problems.
She added: "These families believe their children are
vaccine-damaged and need to know why their children's lives changed so
dramatically within such a short time of the MMR vaccine being given if it
wasn't the vaccine.
"The MMR court cases were vital not only to the families involved in the
pursuit of justice for their children, but for all parents who are concerned
about whether the vaccines they are giving their healthy children are safe."
Ms Fletcher said the UK's vaccine damage compensation scheme was wholly
Solicitors Alexander Harris, representing the families involved in the MMR
battle, expressed disappointment at the ruling.
A spokesman said: "We have been fighting these cases for a number of years and despite many difficulties the evidence has continued to strengthen - and has the support of the international team of experts advising us in the cases.
"We strongly believe in these cases and will be doing our utmost to continue
to move this litigation and the issues forward."
Clare Dodgson, LSC chief executive, said: "I appreciate that this decision will come as a great disappointment to the parents involved.
"I sympathise with their situation. Their children are clearly ill and they
genuinely believe the MMR vaccine caused their illnesses.
"However, this litigation is very unlikely to prove their suspicions.
"It would be wrong to raise their hopes unreasonably by proceeding with this
The LSC has already spent £15m on research into the cases. This would now be submitted to the Medical Research Council, who are looking at the causes of autism.
The Department of Health said they hoped the LSC's decision would "draw a
line" under the MMR issue.
A spokesman said: "We want to see parents given the facts about MMR - that there is no credible scientific evidence showing an association between MMR and autism."
"It remains the best form of protection for your child."