Sales of vegetables are continuing to fall, but help is on the way from takeaways and stores as well as schools and the workplace

Eat more vegetables – it is the constant exhortation from doctors, dieticians and public health experts, but falling sales of greens suggests the advice is being ignored.

This week 30 retailers, cafe chains and catering companies will pledge to include more vegetables in their products. Schools and councils will also be involved, as well as some leading employers who will commit to making it easier for staff to get their five a day.

Greggs, the high street chain known for its pasties and rolls, is among those joining the Pledge for Veg campaign. From January every one of its soups and leaf-based salads will contain enough vegetables to count as at least one of someone’s five a day. From next year, half of all Greggs sandwiches will contain at least half a portion of vegetables and the company plans to sell an extra 15 million portions of vegetables.

Malcolm Copland, Greggs’s commercial director, said it was making the changes after strong sales of its “balanced choice” range showed there was demand for healthier options.

The accountancy firm PwC is one of 30 public and private organisations that will make the pledge for veg at meetings in London, Edinburgh and Cardiff on Tuesday. In partnership with the contract caterer Baxter Storey, which feeds PwC’s 18,000 staff, it will increase the amount of fruit and vegetables available in its canteens and improve the vegetarian and vegan offerings.

“Eating more vegetables has so many benefits. Not only is it healthier for our people and better from an environmental point of view, it’s also on trend for our people who are increasingly interested in vegetarian and vegan options as part of a tasty diet,” said Bridget Jackson, PwC’s head of corporate sustainability.

Obesity is rising and diets low in vegetables are a factor in about 20,000 deaths a year in Britain. Evidence from the Global Burden of Disease project shows that poor diet is the biggest risk factor in Britain for death and disability from diabetes, heart disease and other illnesses. While more people are eating fruit since the five-a-day campaign began running in 2003, sales of vegetables have fallen.

“Most people desperately need to eat more veg but are struggling. Four in five people in the UK want to be eating more. We desperately need the food system to work harder to help us,” said Anna Taylor, executive director of the Food Foundation, one of the organisers of the new campaign.

“These trailblazing pledges are helping to put more veg in the things we’re already buying and eating, at work and on the go, and helping to tackle the food swamps where there is an over-abundance of junk food, and food deserts, with an absence of affordable fruit and veg, which characterise many parts of our cities,” she added.