Parents are being urged to give their children the MMR jab after figures showed measles cases have more than trebled in 11 weeks.

The jab - which protects against measles, mumps and rubella - has proved highly controversial after allegations that it may be linked to autism.

The Government insists there is no link, but take-up of the vaccination has fallen.

Experts fear that infected children returning to school next week may cause measles, which is highly infectious, to spread.

The Health Protection Agency (HPA) said it was difficult to confirm why there had been a jump, but parents not vaccinating their children and lower uptake of the second MMR dose were thought to be factors.

HPA figures show that the number of confirmed cases of children suffering measles is higher than expected for this time of year.

Up until June 10, 136 cases of measles had been confirmed by the HPA.

But only 11 weeks later, the latest figures showed this had more than trebled to 480 confirmed cases. Of these, there were 49 in Yorkshire and Humberside, but only one in the North-East.

In the whole of 2006, there were 756 cases, which was the highest year on record.

More samples are arriving in HPA laboratories every day with about half testing positive.

Measles, which can be life threatening and cause severe disabilities, is most common among children aged one to four who have not been immunised, but can strike older children and adults too.

Babies are given the first dose of the MMR jab when they are about 13 months old and the second jab between the ages of three-years-four-months and five, according to the Department of Health.

The second jab is vital to keep immunity rates high.

After the first dose, between five and ten per cent of children are left unprotected from the diseases, but this falls to less than one per cent after two jabs.

Symptoms of measles include a high temperature, cough, runny nose, and red and watery eyes, with a rash of spots appearing over the next few days.

An HPA spokeswoman said it was too early to say whether 2007 would prove to be the highest year on record since monitoring began in 1995.

However, she sad the current figures showed it was following the trend set last year.

Dr Mary Ramsay, a consultant epidemiologist at the HPA, said: "Over the summer holidays, we have seen more cases of measles being reported than we would normally expect.

"This means it is crucial that children are fully immunised with two doses of MMR before they return to school.

"Measles is a highly infectious and dangerous illness and, as there is increased close contact in schools, it can spread easily.

"Now is the time parents will be buying their children a new school uniform to prepare for the school year ahead, but being prepared to avoid infection is even more important.

"Parents should think about adding the MMR vaccine to their back to school 'to do' list."

The HPA said a high number of cases has been noted in communities where vaccine uptake is lower, including travelling families.

But cases were also currently occurring in unvaccinated school-age children across all social groups.