"Markets are a mode of food supply going back more than eight centuries that has to come back," he told guests at a City of London markets committee dinner last week. The city runs New Spitalfields Market, claimed to be the UK's largest horticultural wholesale market.
Lang said such markets offer an alternative to the supermarkets, which dominate food selling. "The reflex is to leave food policy to Tesco et al, but they can't deal with this big agenda."
He added: "They are coming back into towns, but are still using an unsustainable model. A quarter of lorries on the road are carrying food and a quarter of the wagons are empty.
"Sainsbury's chief executive Justin King told me he thinks that little tweaks here and there can bring the necessary changes. But in 10 years' time we will have to change people's behaviour," Lang insisted
He warned: "We have a new confluence of events and pressures that are intensifying and huge uncertainty. There are definite tough times ahead."
Lang, who is also a trustee of London's Borough Market, argued that the corporation has to carry out a dramatic rethink to meet the challenges this poses.
Development scheme Funding withdrawn
The London wholesale markets' business development manager scheme has ended after the Greater London Authority withdrew funding.
The scheme, involving Western International Market, New Spitalfields Market and New Covent Garden Market, aimed to provide growers with an alternative market to the major retailers. Managers claimed that it generated £20m of new business for each of the three years it ran. But no alternative funder has come forward.