As a global consensus emerges on the food crisis, politicians must get real, says Tim Lang

Last week I heard the City Food Lecture by Paul Polman, CEO of Unilever, in the medieval splendour of London's Guildhall. And this week I attended the launch of the UK chief scientist's 'The Future of Food and Farming' report at HM Treasury.

One was a giant food corporation thinking out aloud. The other was a collation of scientific evidence. In the best of senses, neither said anything dramatically new, but both left their comfort zones.

One mapped new corporate governance. The other challenged governments to deliver joined-up policies. Both focused on the developing world. Both recognise but didn't confront the shockingly deep footprint we Westerners impose on Planet Food.

The frustration is palpable. Everywhere except in governments, people are stirring, knowing the food system is in serious trouble. But is anyone in charge? Mighty Unilever (or any of the giants now worrying) cannot resolve climate change any more than a collation of scientific evidence leads to policy.

The pressure mounts. In 2008 we had major World Bank and Chatham House reports. Last October, the Australian chief scientist's, then INRA's (France), and now Foresight's (UK). How much evidence is needed? How high the prices and political destabilisation?

A consensus is emerging that current food systems cannot go on. Yet world food policies still broadly remain the same: leave it to markets; tweak a bit; don't frighten consumers; efficiency will do it.

Not enough. There's no overall policy grip. Yet that's needed. Even 'ordinary' consumers are aware that something is wrong but unsure what to do. Change a few light bulbs here, eat a low-fat product there, buy the odd Fairtrade product. These are positive signs of willingness to change, captured in the Sustainable Development Commission's influential 'I Will if You Will' report.

The policy mix of the past few decades is in the shredder. Single solutions aren't enough. GM won't crack culture change. Nudge psychology won't alter Western over-consumption. Oil won't stop running out with a few billion low-carbon crisps. Water won't flow to the desert if we reduce embedded water in milk chains.

The ball is firmly in politicians' court. My experience is that nothing will happen unless there is concerted pressure (or war or shock). 'Twas ever thus.

Tim Lang is professor of food policy at City University