Greengrocers are set to grab a share of a £129m a year windfall, thanks to a government initiative.

Healthy Start is a Department of Health scheme that gives families vouchers to spend on milk and, for the first time, fruit and vegetables.

A trial in the southwest found it boosted fresh produce purchases, especially in the high street. It goes nationwide next week. Pregnant mums and families with young children and a low income will be given vouchers worth £2.80 a week to purchase fresh produce, milk and infant formula.

Healthy Start, which costs £129m per year, replaces the Welfare Food scheme, which enabled the purchase of milk alone. Government researchers say that 22% of the money is spent in independent and high street shops and 63% in the multiples. This is a bonus for independents, which typically have a much smaller share of overall sales.

The extension of the scheme will see the vouchers being used in more than 18,000 outlets nationwide, compared to just 1,000 in the south-west trial. And it should encourage people to buy more produce.

"We cannot break down costs between milk, fresh produce and infant formula," said a Department of Health spokeswoman. "But in Devon and Cornwall, qualitative surveys of small numbers of beneficiaries suggested that some were now buying more fruit and vegetables."

Retailers have been quick to sign up for the scheme. Southwest greengrocery chain Stokes said its 15 participating stores received about 150 vouchers a week. "We will definitely extend it to our other stores. It has been quite good for us, encouraging people to spend money in the high street," said marketing manager Andrea Harris.

Guy Watson, MD of Riverford Organics, the vegetable box delivery firm, said: "We're rolling it out more widely. I'm all for extending our boxes to lower income families."