Three-quarters of the Welsh population's recommended daily intake of vegetables should be grown in Wales by 2030, food experts have urged.
Food Policy Alliance Cymru said this could be achieved in a sustainable way with more support for small-scale horticulture farms and gardens.
Rules around the procurement of food by schools and other public bodies could also be reviewed to push local produce.
The Welsh Government said it funded advice and training for businesses.
Currently less than 0.1% of Wales' land is used to grow vegetables.
If what is produced in the country at present had to be shared out to everyone in Wales, it would only equate to a quarter of a vegetable portion per person each day, a recent study suggested.
Public Health Network Cymru recommends people eat at least five portions of fruit and vegetables a day.
Campaigners said scaling up production would bring benefits for health and the rural economy and reduce reliance on imports, while helping address climate change.
They want to see an independent food system commission set up to oversee a "major transformation" in what we grow and eat.
The group - made up of environmental charities, agricultural organisations and academics - has presented its ideas in a manifesto for the political parties ahead of May's Senedd election.
Katie Palmer, programme director at Food Sense Wales and a member of the alliance, said there had to be a "big push" to improve people's diets and added the climate crisis meant changes were needed to how food was sourced.
"Not only are we not eating enough vegetables, we're not producing enough," she said.
She said Wales had a "very fragmented horticulture sector", with not enough financial support available to help the "lots and lots of small-scale" businesses and charities to increase production.
The group also wants changes to school lunches, which are currently under review, and more public procurement of local produce.
Public Health Wales has reported that less than a third of adolescents eat a portion of vegetables once a day.
The campaigners claimed moving to recommending two portions of vegetables per child each day in school could generate a 44% increase in domestic horticulture production.
Isla Horton, director of Grow Cardiff, which supports horticulture projects across the city, such as the Riverside Community Garden, said a skills shortage also needed to be addressed by "embedding growing into the school curriculum".
"We have to create a culture of growing where people know how to do it - we've lost that to some extent in Wales," she said.
The manifesto also calls for Wales to eliminate the need for foodbanks by 2025.
The food system should also be "net zero" - not adding to the emissions driving global warming - by 2035 - with farms encouraged to adopt methods to restore biodiversity and fight climate change.
Government advisers at the Climate Change Committee have also suggested Welsh farmers get support to transition to growing crops as part of subsidy reform.
A taskforce set up by the Welsh Government to ensure a green recovery from the coronavirus pandemic has recommended boosting horticulture.
Farming leaders said it could be difficult to scale up vegetable production significantly in parts of the country, because of the nature of Wales' agricultural land.
What do the political parties say?
The Labour-led Welsh Government said it wanted to create "one of the most environmentally and socially responsible supply chains in the world", and has provided support for the sector via the Farm Business Grant, Farming Connect, Tyfu Cymru and Horticulture Wales Business Clusters.
The Welsh Conservatives' environment spokeswoman Janet Finch-Saunders MS said she wanted a better system of support for community gardens, plans "to make orchards of underutilised publicly-owned green spaces", and the introduction of a local food and drink charter to encourage retailers to sell locally-sourced Welsh produce.
Llyr Gruffydd MS, Plaid Cymru's environment spokesman said his party would introduce a food commission if elected.
He said a "whole system approach... that encompasses the environment, health, economy and poverty" was needed.
Welsh Liberal Democrat agriculture and food spokesman William Powell said he strongly welcomed the alliance's manifesto and that increasing the volume of vegetables grown and sold in Wales would reduce the reliance on imports and boost local economies and farmers.