Tory plan to 'curb' supermarkets
Both parties say food diversity must be protected
The Tories say they plan to introduce a new supermarket ombudsman to support the interests of farmers against abuses of power by large food retailers.
The ombudsman would settle disputes between retailers and suppliers.
The Tories will announce the idea at the Oxford Farming Conference, as they call for a "new age of agriculture".
Labour is due to launch its own food strategy, with ideas such as "meat free" Mondays, more allotments and a bid to cut waste and reduce emissions.
In a speech to the conference, Environment Secretary Hilary Benn will point out that methane produced by ruminant livestock accounts for 4% of the UK's total carbon emissions.
He will urge farmers and food producers to do more to reduce their carbon footprint while urging consumers to be more aware of how food is produced and its environmental impact.
In its updated food strategy, the government acknowledges calls by some campaigners for people to eat less red meat to protect the environment but says the evidence needed to back this up and to provide appropriate advice to consumers is "currently unclear".
Mr Benn will also pledge to do more to combat obesity, suggesting smaller portions of high-fat food.
He also wants to make it easier for people to lease land to grow their own vegetables as way of reducing the long waiting list for city-centre allotments.
It is not enough to talk loosely about a fair market or the need for better labelling
Shadow environment spokesman Nick Herbert
Addressing the same event, shadow environment spokesman Nick Herbert will say the voluntary code of practice governing the relationship between supermarkets and food suppliers is not "worth the paper it is written on" unless properly enforced.
"It is not enough to talk loosely about a fair market or the need for better labelling," he will say.
"We need action, with a supermarket ombudsman and legislation to enforce honest labelling if the retailers won't act."
Following a long-running inquiry, the competition authorities concluded in 2007 that the supermarket industry was operating in the public interest and leading retailers such as Tesco were not overly dominant.
But they called for an ombudsman to resolve disputes and ensure retailers did not exploit relationships with suppliers to push through unfair or retrospective contractual agreements.
"Failure to do so could result in reduced investment by suppliers, lower product quality and less product choice, with potentially higher prices in the long run," Mr Herbert will add.