The measures - due to be announced in spring following consultation with the food industry - are part of targets to reduce calories in every day foods by 20 per cent.

They follow Government pledges to halve rates of childhood obesity by 2030.

Dr Tedstone said it was not enough for restaurants to offer healthy options, saying Britain’s weight problem would only be tackled if the calorie content of most foods was cut.

She told The Telegraph: “It could mean less meat on a pizza, it could mean less cheese, it could mean a smaller size. Consumers are saying they want smaller portions and healthier options.”

“We know that just having healthy options on the menu won’t change the nation’s habits - we need the default option to have fewer calories. The default options for pizzas are margherita and pepperoni pizzas, so we need them to get healthier.”

Officials said the proposals were at an early stage, with discussions in coming months to decide what is “feasible and achievable” before decisions are made.

Under current plans, the limits would not be mandatory, but similar targets for sweet foods - which have seen a 2 per cent fall in sugar, against a target of 5 per cent - have prompted warnings from ministers that tougher steps may be taken.

Public Health Minister Steve Brine said the Government was “willing to do whatever it takes to keep children healthy and well in this country.”

Research shows one in five meals are consumed outside the home, with today’s children spending at least twice as much time eating out as those who grew up in the 1970s.

The proposals are part of a Government childhood obesity plan which has proposed calorie counts on restaurant menus, a ban on advertising of unhealthy foods on television before the 9pm watershed, and the removal of such goods from checkouts and two-for-one deals.

Eustace de Souza, national lead for children at PHE, said firm measures were needed to tackle Britain’s growing obesity problem.

New statistics from a national programme to weigh and measure children show that 20.1 per cent of pupils leaving primary school are obese. The figure, from NHS Digital, is a rise from 18.7 per cent when children began being measured in 2009/10.

And 4.2 per cent of children leaving primary school are now classed as “severely obese” - compared with 3.2 per cent in 2006/7 - and just 0.4 per cent in 1990.

Mr De Souza said the trends were “disappointing”.

“This shows why the government is taking drastic action; there are no grounds for complacency,” he said.

Children are deemed severely obese if they are above the 99.6th percentile on growth charts from 1990, which were based on typical measurements at the time.

Calorie counts in common pizzas:

• Domino’s Pepperoni Passion classic crust - 1212 calories

• Goodfella's Deep Pan Pepperoni Pizza  - 1028 calories

• Pizza Express American - 1019 calories

• Pizza Hut Pepperoni classic - 1050 calories

• Pizza Express Margherita - 834 calories