The Government is renewing its efforts to ensure children up to the age of 18 receive the MMR jab.

The Department of Health is making extra doses of the vaccine available and pledging more cash to help NHS trusts vaccinate youngsters.

Trusts in London will receive an extra £60,000 while those outside London will get £30,000. The last time a similar campaign was launched was in 1994.

The MMR jab, which is designed to protect against measles, mumps and rubella, has proved controversial.

In 1998, a study published in respected medical journal The Lancet suggested a link between the jab and autism and bowel disease.

News of the link - which has since been dismissed by experts - led to coverage rates falling as parents refrained from giving their children the jab.

Chief medical officer Sir Liam Donaldson has written to all primary care trusts asking them to help cut the risk of a measles epidemic.

He wants PCTs to urge parents to get their unprotected children immunised.

Across the country, the number of cases of measles is on the rise. There were 1,726 confirmed cases in England and Wales in 2006 and 2007 - more than the previous decade put together.

From 1996 to 2005, there were a total of 1,621 confirmed cases of measles in England and Wales.

Estimates suggest about three million children aged between 18 months and 18 have missed either their first or second dose of the MMR jab.

After the first dose, between 5% and 10% of children are not protected against the diseases. After two doses of MMR, this falls to less than 1%.

The first dose is given to children at around 13 months of age, with a booster dose given before they start school.

Experts have warned the Government and the Health Protection Agency that uptake needs to improve urgently.

Prof David Salisbury, director of immunisation at the Department of Health, said: "Parents who have not had their children vaccinated with the MMR vaccine should do so now."

Estimates suggest a measles epidemic in Britain could result in 30,000 children and young people being affected, or 100,000 in a worst case scenario.

Patricia Hamilton, president of the Royal College of Paediatrics and Child Health, said: "We cannot stress too strongly that all children and young people should have the MMR vaccine.

"Overwhelming scientific evidence shows that it is safe."

Measles is caused by the rubeola virus, and contracting it can result in some severe, but rare, complications.

These include meningitis, pneumonia, encephalitis, low platelet count and bronchitis. Measles in pregnancy can be fatal to unborn babies.

The World Health Organisation has set a goal to globally eradicate measles by 2010. This will require 95% of the world's population to be immunised.