In an extraordinary intervention, Andrew Wakefield, who was struck off the medical register, said the “British Government is entirely culpable” for the outbreak and accused officials of “putting price before children’s health” – despite a widespread consensus that it was the panic over his flawed research that led to the surge in the disease.

The number of measles cases in the Swansea area rose to 693 on Thursday. It is now the largest outbreak in the country for over a decade, exceeding the 622 cases recorded in Merseyside in 2012.

Public Health Wales warned that the outbreak was unlikely to peak for “two to three” weeks because of the incubation period for measles. Children return to school after the Easter holiday on Monday and will begin mixing with a wider group of their peers, which could accelerate the spread of the disease.

Health officials urged parents to take their children to one of the drop-in vaccination clinics set up in the wake of the outbreak.

They say at least 6,000 people remain unprotected in south-west Wales and it is only a matter of time before a child develops serious complications as a result.