Video report by ITV News Correspondent Stacey Foster
Labour's Deputy Leader has urged McDonald's to drop its "Monopoly" prize draw, branding it "a danger to public health".
Tom Watson labelled the fast food chain McDonald's annual promotion a "grotesque marketing ploy" which he said was helping to feed the UK's obesity crisis by encouraging people to eat unhealthy food.
The competition, which starts on March 20, allows customers to win free food from its restaurants as well as bigger prizes including a Mini cooper and £100,000 in cash.
Mr Watson wrote to McDonald's UK asking for the competition to be cancelled.
The letter states: "It is unacceptable that this campaign aims to manipulate families into ordering junk food more frequently and in bigger portions, in the faint hope of winning a holiday, a car, or a cash prize many would otherwise struggle to afford", the Observer reported.
One in three children leaves primary school overweight or obese and the number of children classed as seriously obese is at a record high according to the Department of Health and Social Care (DHSC).
Barbara Crowther, a spokesperson for Children's Food Campaign, told ITV News that the campaign encouraged people to "gamble with their own health".
A McDonald's UK spokesman said: "This year's Monopoly campaign sees customers receive prize labels on carrot bags, salads and our Big Flavour Wraps range and we have removed the incentive to 'go large', providing the same number of prize labels and chances to win on a medium meal as you get on a large.
"Nutrition information is clearly displayed online, on our app, in restaurant and across our packaging and we continue to review, refine and reformulate our menu to reduce saturated fat, salt and sugar."
Mr Watson's criticism of the fast food chain's latest marketing gambit comes as the government announced plans to ban junk food adverts on TV and online before 9pm were being put out for a public for consultation.
Junk food adverts during children's TV shows have been banned since 2007 but research by broadcasting regulator Ofcom claimed youngsters spend 64% of their TV viewing time watching shows not aimed specifically at them.
Public Health Minister Steve Brine said: "The NHS is already preparing to treat more and more children for the serious effects of extreme obesity in the future, so we have a duty to address the underlying causes because we believe passionately in our NHS."
Up to 1,000 more children per year are expected to require treatment for severe obesity-related problems like diabetes and asthma by 2022-23, the DHSC said.
It has previously called the current situation a "rising epidemic in childhood obesity".
Campaigners, doctors and politicians welcomed the proposal.