Labour is to push for a national law to ensure that new policy decisions are gauged against people’s future health and wellbeing, with an ambitious idea modelled on similar schemes already in place in Wales and New Zealand.

The proposed Future Generations Wellbeing Act for England, to be unveiled on Saturday by the shadow health secretary, Jonathan Ashworth, would mandate measures such as a “health equality audit” of all government decisions, and put a new duty on local health services to reduce health inequalities.

Other elements of the proposed act, which the party plans to consult upon, would ensure health measures were linked to environmental and climate emergency goals, and to recognise the NHS as what is called an “economic anchor” in communities.

In 2015, the Labour government in Wales introduced its own Wellbeing of Future Generations Act, which requires decisions to be measured against a range of long-term outcomes, including public health, the environment and social cohesion.

While that law has faced criticism for a perceived lack of efficacy in challenging decisions, it was seen as playing a part in the Welsh government’s decision to scrap plans for a new section of the M4 motorway near Newport.

In New Zealand, the Labour government of Jacinda Ardern said it would plan future national budgets around the concept of wellbeing. The first of these, published in late May, included billions of dollars for mental health services and child poverty as well as record investment in measures to tackle family violence.

Ashworth, who will announce the plan for the new English law at the Fabian Society’s conference in London, said there was a broad background to the idea. “The context is all sort of things happening in health, like life expectancy going backwards, health inequalities getting wider, infant mortality rates getting worse for three years in a row. We basically need a new approach,” he said.

“If you judge things by wellbeing it can lead to some pretty radical outcomes, or at least different ones to those you expect. It’s not just rhetorical. And we need something like this at a Westminster level.”

In his speech, Ashworth was also due to announce a plan to commit almost £27m to a programme intended to help provide children in deprived areas with fresh fruit and vegetables.

The scheme – called Healthy Start – already exists, but Labour said figures show the number of women and children eligible to receive vouchers under it has fallen by 20% in four years.

Ashworth was to say in his speech: “We will focus determinedly on improving the health and wellbeing of every child, ensuring children have access to nutritious food not just in schools but also by expanding Healthy Start. Labour will ensure the poorest children receive the milk, fruit and vegetables they need.”