Dave Lewis worked for consumer goods group Unilever for 27 years before joining Tesco as chief executive in 2014. He is stepping down on Oct. 1 and will be succeeded by Ken Murphy, a former executive of Walgreens Boots Alliance.

Tesco has a 27% share of Britain's grocery market.

"What's clear to me is that we do not take a whole-society approach to food," Lewis wrote in an opinion piece published on the FT Online website.

"We face the worst public health crisis in generations. Economic contraction threatens the livelihoods of millions. And the point of no return on climate rapidly approaches," he said.

Lewis said the government-commissioned independent review of a UK national food strategy, which will soon publish its first report, must address these issues.

"But heavy-duty change cannot be left to the market. The right regulatory context, access to capital and incentives to innovate are critical."

Lewis said previous governments had missed opportunities for change.

"The UK's industrial strategy didn't focus enough on food despite the food and farming industry being worth 122 billion pounds," he said.

Lewis said land needed to be used more efficiently, soil health improved, forests and habitats protected, carbon emission targets met, animal welfare and food safety standards upheld through trade negotiations and more healthy eating encouraged.

"There is a new context now. Covid-19 cruelly exposes the relationship between obesity and health outcomes. Brexit creates the opportunity to reshape production and standards. A growing consensus across business points to willingness to act on climate," he added.

(Reporting by James Davey; Editing by Steve Orlofsky)