Britain is on the brink of an epidemic of childhood diseases because parents are shunning the MMR jab for their children, public health experts warned last night.

Government figures reveal a fivefold increase in mumps and a doubling of measles cases in the past year. The statistics coincide with the disclosure that the uptake of the mumps, measles and rubella (MMR) vaccine is at an all-time low.

Dr Vivienne Nathanson, head of science and ethics at the British Medical Association, said: "These figures are extremely worrying. We are now at the danger zone, where instead of having small, sporadic outbreaks we are going to get major epidemics which could well become lethal ... that could happen very quickly."

Between April and June there were 467 cases of mumps, compared with 84 confirmed reports for the same period in 2002, the Health Protection Agency (HPA) reported.

Measles cases more than doubled, from 52 in the second quarter of 2002 to 145 during the same period this year.

MMR immunisation rates are at their lowest, with 78.9 per cent of children receiving the vaccine, despite a £13m government campaign to convince parents that MMR is safe.

The World Health Organisation says that 95 per cent of children need to be vaccinated to ensure "herd immunity" protection for the whole population.

Experts say that the situation is reaching a crisis point, with thousands more children back at school with no protection against diseases that could prove lethal.

The crisis of confidence over MMR safety is entering its fifth year, with uptake in some parts of London as low as 70 per cent. Tony and Cherie Blair have been criticised for refusing to say whether their son Leo, aged three, has been given the jab.

Dr Nathanson said more forthright tactics were needed to avert major outbreaks of mumps and measles.

She said: "If we do not see MMR uptake rising, the epidemics will become self-sustaining and permanent because there will always be somebody who is ill, or infected or infectious. We need to make parents see how dangerous these diseases are. I am not saying we should frighten them but we need to start saying to them, how guilty would they feel if their children got one of these illnesses and was seriously damaged or even died?"

Measles can cause blindness, brain damage and death in severe cases, while mumps can cause infertility in teenage boys. Many of the mumps cases are occurring in teenagers, who were born before MMR was introduced, but who should have been protected by the "herd immunity" provided by younger children.

A spokeswoman for the HPA said: "We are seeing local outbreaks in areas of the country where MMR uptake has dipped or been low for longer periods of time. We are concerned that, if this pattern continues, the increasing number of unvaccinated people could lead to an increase in the number of susceptible children.

"This is why it is vitally important to reassure parents that MMR is the safest and most effective method of protecting our children."

The controversy began in 1998, when Andrew Wakefield, a researcher at the Royal Free Hospital in London, published a study linking MMR with autism and bowel disease in children. Several studies have since discounted the link, but hundreds of families now claim that their children have been damaged by the vaccine.

Legal action against the manufacturers of the vaccine is due to be heard at the High Court in London next year.

Ministers have refused to allow single vaccines to be made available on the NHS, insisting that MMR is the safest way to immunise children. Private clinics offering the separate jabs say the red tape involved in acquiring the vaccines means they are constantly running low on supplies. MMR made headlines again in June when a High Court judge ruled that two children should be given the vaccine against the wishes of their mothers.

The Government said yesterday that figures showed MMR uptake was stabilising. Melanie Johnson, a Health minister, said: "The figures show that the overwhelming majority of parents and carers are choosing MMR as the best way to protect their children from these serious diseases."