Parents were today warned of the dangers of a possible measles outbreak because fewer children are being immunised.

Health experts fear the disease could reapear as thousands of pupils in Sussex return to school for the start of the new term.

There has been a drop in the number of children being vaccinated with the MMR (measles, mumps and rubella) jab in West Sussex in the last two years.

The average figure for East Sussex has stayed the same although there was a slight drop in the Brighton, Hove and Lewes area.

In 1998/9 89.2 per cent of children in West Sussex were vaccinated compared to 92.8 per cent the year before.

The average number of children vaccinated in East Sussex last year is 86 per cent with the lowest take up in Brighton, Hove and Lewes at 79.3 per cent.

This is in line with the national trend highlighted by Shadow health secretary Liam Fox today who warned failure to immunise could lead to the rapid reappearance of the disease up and down the country.

Mr Fox said: "I am particularly worried about the lack of progress on the measles vaccine, as a result of which children are more vulnerable than in recent years."

Experts believe the drop is linked to health scares associated with the vaccine which have linked it to autism and bowel disorders.

Both East Sussex Brighton and Hove and West Sussex health authorities, today stepped in to reassure parents that no outbreak was expected.

But they recommended all parents should get their child vaccinated as a precaution.

Angela Iversen, consultant in comminicable disease control in East Sussex, said: "Measles is highly infectious and obviously the fewer parents who take up the offer the more chance there is of the disease reoccuring.

"We work closely with GPs and practices to give out as much information about the jab as possible and we always recommend it is used."

A spokesman for West Sussex Health Authority said: "The best way to prevent measles is to vaccinate all the community using the highly effective MMR jab.

Campaigners against the MMR vaccine were unhappy with Mr Fox's announcement.

Isobella Thomas, from Justice Awareness and Basic Support (JABs) said parents deserved to have the choice.

She said: "Parents can choose to have a single vaccine instead of the combined one but that is only available privately.

"We think it is unfair that parents are not given any option without having to pay for it.

"I have two children who were damaged by the MMR vaccine when they were young and I will continue to campaign to make sure parents are made fully aware of the risks."

Mr Fox said he hoped lessons would be learnt from the dramatic reduction in the number of meningitis C cases, achieved through an extensive vaccination programme.

A spokesman for the Department of Health said: "This is a safe vaccine and we would urge parents to have their children immunised. It is never too late to have the jab.

John Grounds, director of Horsham-based charity Action Research, said: "It is generally considered that measles is a threat of the past in this country but this is only due to the comprehensive vaccination programme that is in place.

"We would urge parents to seriously consider the huge risks associated with not having their children vaccinated."