Parents are increasingly opting for single vaccinations

Parents had taken their children to the clinics because they wanted them to be given separate jabs.

The Department of Health has told GPs all affected children should be given the MMR jab to ensure they are protected from the diseases.

The two clinics concerned are at Elstree Aerodrome in Hertfordshire and Hillsborough Arena in Sheffield.

Up to 40,000 immunisations given there over the last 10 years may not have been properly administered, the Department of Health said.

We really do believe that the safest and most effective way for parents to put this right,is for their children to have the MMR vaccination Dr David Salisbury

As concerns have grown over the safety of the combined measles, mumps and rubella jab, increasing numbers of parents have been choosing single immunisations for their children.

Figures from the Health Protection Agency show that the uptake of the MMR vaccine had fallen to 78.9% across England and Wales in the first quarter of this year.

Vaccination levels must reach 95% if they are to create a so-called "herd immunity" to protect children from outbreaks.

Restrictions

Concerns over the Hertfordshire and Sheffield clinics were first raised last year.

Experts then thought around 1,000 could have been received vaccines which were not properly made up or administered during the second half of 2002.

Dr David Pugh ran the clinics

But an investigation has now revealed that problems had begun up to 10 years ago.

Investigators have been unable to obtain a comprehensive list of children who were vaccinated at the clinics.

A media and advertising campaign is now being launched to alert parents who may have used the clinics to the potential problems.

The clinics have now been closed by the National Care Standards Commission because they were not properly registered.

The General Medical Council has imposed restrictions on Dr David Pugh, the doctor who ran the clinics under the name of Lifeline Care, which mean he is no longer allowed to give vaccinations.

He is now believed to be in Australia.

Preparation

Dr David Salisbury, the head of the government's immunisation and communicable disease team, told the BBC the clinics had made up batches of the vaccines in advance, against manufacturer's guidelines.

"The vaccines were made up in a way which was quite contrary to all of the recommended techniques.

"What this does is raise questions about whether the vaccines are still effective when they have been made up so incorrectly."

It is recommended that doses of the vaccines are made up individually before being given to children.

Dr Salisbury said it was also possible that the vaccines could have become contaminated because of the way they were prepared.

"This could have increased the risk of children suffering bacterial infections from the immunisation or greater side effects to the vaccines."

He said: "Some children who have been vaccinated may not be adequately protected against one or more of the diseases for which they received the vaccine."

Dr Salisbury added: "It will be difficult, because parents chose to have single vaccines for their children, but we really do believe that the safest and most effective way for parents to put this right is for their children to have the MMR vaccination."

Protection

A Department of Health spokesman said: "We are advising parents of children who received a single vaccine at these clinics to contact their family doctor.

"They should not be alarmed, but they do need to ensure that their children are protected against measles, mumps and rubella."