The BBC's Niall Dickson reports: "Many parents are concerned and confused"

"If parents don't have their children vaccinated . . . we will see the return of three diseases which in the past have caused serious illness and even death," he told the BBC's Nine O'Clock News.

"There is a serious danger if levels of immunisation continue to fall that we will see a resurgence of epidemics of these three diseases."

Off-target

Currently 87% of Britain's population is immunised, below the World Health Organisation's 95% level preferred to keep the diseases under control, Dr Donaldson said.

Liam Donaldson warning of an epidemic

A much-publicised and highly controversial theory put about in the early 1990s, drew a link between the single-jab vaccine for the three diseases and autism and bowel disease.

Although there was little strong evidence for the theory and much larger studies have since shown there to be no such link, some parents refused to let doctors give their children the injection.

At the time, doctors warned that the dangers of not having the vaccine were far greater than any theoretical risk of autism or bowel disorders.

As immunisation rates dropped off by 10% following the scare, they feared the return of the three diseases that had taken so long to bring under control.

Some doctors have suggested that the vaccine be made compulsory, considering the potentially devastating effects of the diseases.

Dr Donaldson is the latest figure to add his voice to the debate.

Serious effects

As recently as the early 1980s, measles was killing about 17 British children a year.

The MMR vaccine has been declared safe

However, it is more likely to lead to serious complications, particularly in the very young.

These can include pneumonia or bronchitis, convulsions, and even meningitis.

Mumps, characterised by painful and swollen glands in the head and neck, can cause permanent damage to the testicles, nervous system and hearing.

And rubella, or German Measles, if developed late in pregnancy, can lead to serious birth defects such as deafness, blindness, cardiac problems and brain damage.

The MMR vaccine, made from weakened versions of the three viruses, was introduced in 1988 and virtually eliminated measles, which had already been halved by the introduction in the 1970s of a single measles vaccine.