Fewer children in Sutton and Merton have been vaccinated against the potentially fatal diseases of measles, mumps or rubella by their second birthday than anywhere else in the country.
Just 78.7 per cent of children under the care of Sutton and Merton PCT, now defunct, received their first MMR jab by their second birthday in 2011/12- the lowest percentage recorded by any primary care trust (PCT) in the country.
The London average is 86.1 per cent, again the lowest of any region in the UK. By the time a child reaches the age of five, 77 per cent of children in Sutton and Merton had received both MMR jabs - the 13th lowest uptake in the country.
Ten of the lowest scoring PCTs were in London boroughs with Croydon ranking joint third lowest in the country with Hammersmith and Fulham.
The figures, from the Health and Social Care Information Centre, come following an outbreak of measles in south Wales which left one man dead and 800 infected.
Councillor Suzanne Evans, conservative deputy leader and chairman of Merton’s health and scrutiny panel, said: "Thankfully we’ve not had a measles outbreak in Merton, and let’s hope we don’t.
"However the harsh fact remains that as we have one of the lowest levels of uptake of the MMR vaccine, we are clearly at high risk.
"The MMR jab is safe - measles is not."
Merton Council is now responsible for encouraging parents to vaccinate their children after changes to the health service on April 1 and is urging parents to check with their GP that their children have received both MMR vaccinations.
A first dose is given to a child from the age of one with a second booster dose needed to ensure greater prevention.
Councillor Maxi Martin, cabinet member for children’s services said: "We take the health and well being of our children and young people very seriously, and the transfer of public health to the borough will help us encourage and support the take up of all vaccinations by parents."
Dr Kay Eilbert, the council's director of public health, said: "Increasing immunisation take up will be a key priority in my new role and I will be working with Merton's health providers, schools and children's centres to improve access to information and vaccinations."