The High Court rejected an application for a judicial review of an earlier decision to deny them public funding.

Hundreds of parents are involved in the case. They claim their children developed problems after having the controversial jab.

But no studies have proved a link, and most experts say the vaccine is safe.

Public money

The Legal Services Commission ruled last year that it would be wrong to spend £10m of public money on the action.

An independent funding review committee upheld that decision in October.

The children involved in this case have a range of disabilities, including autism, bowel problems, epilepsy and other learning difficulties.

Some parents are now considering taking their legal campaign to the Court of Appeal.

Isabella Thomas of Justice Awareness and Basic Support said: "We will fight on to the end. This doesn't stop us because we have to have justice.

"Parents are willing to sell their homes. Our children's lives are at stake. To watch your child in such severe pain is dreadful."

Others say they will pursue their fight through the courts without legal aid.

"I will do everything to the best of my ability to continue the litigation," said Jennifer Horne-Roberts, one of the parents involved in the case. "I shall represent people pro bono."

Announcing his decision, Mr Justice Davis, sitting in London, said there was no legal reason to overturn the decision to deny the parents legal aid.

"In my view the decision of the funding review committee was proportionate.

"It was rational, it took into account relevant considerations, it was sufficiently reasoned and there was no procedural unfairness.

"None of the various public law challenges advanced have been made good," he said.

The judge said he could "well appreciate the decision to withdraw legal aid will have caused great dismay to the parents of the claimants".

But he added: "The decision to withdraw legal aid funding from the claimants stands."

Clare Dodgson, chief executive of the Legal Services Commission, welcomed the ruling.

"I have every sympathy for the parents. Their children are clearly ill and they genuinely believe the MMR vaccine caused their illnesses.

"However, I am not convinced that legal action is the best way of deciding this matter."

The ruling comes a week after the medical journal The Lancet said it should never have published a controversial study, which suggested the three-in-one jab was linked to autism and bowel disease.

The General Medical Council is now carrying out an investigation into Dr Andrew Wakefield, the doctor who led the 1998 study.