Last month, they lost the final battle in one effort, which claimed that the measles-mumps-rubella (MMR) vaccine causes autism.

FORBES: Vaccine Court Ruling: Thimerosal Does Not Cause Autism

The ruling came from a panel of "special masters" who began hearing three test cases in 2007 involving children with autism -- a disorder that their parents contend was triggered by the vaccine against measles, mumps and rubella combined with vaccines containing thimerosal, a mercury-based preservative.

CNN: Vaccines didn't cause autism, court rules

Speaking on Wednesday, Mr Blair urged parents to ignore media "scaremongering" as he repeated government advice that the vaccine against measles, mumps and rubella - which has been linked to autism - is safe.

BBC: Blair signals support for MMR