Almost two thirds of NHS trusts have already signed up to a voluntary scheme to slash sales of sugary soft drinks, milkshakes and hot drinks with added sugar syrups.

Health chiefs want sugary drinks to make up less than 10 per cent of drinks sold in hospitals.

But 91 trusts are yet to join the programme, and hospitals and suppliers have been warned a ban will be introduced next year if they don’t take action by March.

NHS England chief executive Simon Stevens, said: “It’s important the NHS practices what it preaches on healthy food and drink.

“We want 2018 to be the year when the tasty, affordable and easy option for patients, staff and visitors is the healthy option.

“Many NHS hospitals have answered the call and are taking positive action.”

Some 14 national suppliers, including WH Smith, Marks & Spencer and Greggs have signed up to the NHS voluntary scheme along with 141 of 232 trusts.

Derbyshire Healthcare NHS Foundation Trust banned sugary drinks two years ago, while Northumberland, Tyne and Wear NHS Foundation Trust has only sold non-sugar sweetened beverages in its seven cafes, two shops and vending machines since January this year.

Public Health England chief executive Duncan Selbie said: “Hospitals should play an important role in preventing obesity, not just treating it.

“Plans to offer healthier food and restrict less healthy options are a positive step towards tackling the country’s obesity problem.”