This week at the Oxford Farming Conference I announced that a Conservative Government would appoint a supermarket Ombudsman to ensure fair dealing with suppliers.
Supermarkets have sometimes used their considerable power to engage in sharp practices, for example retrospectively demanding lower prices from farmers.
The Competition Commission has warned that this can lead to less investment and innovation by producers, which in the long term damages the consumer interest - and could lead to higher prices.
Supermarkets are a controversial local subject. When Tesco arrived in Pulborough, bringing a second major store in the village in addition to Sainsbury's, people worried about the impact on local shops.
Supermarkets are popular. We all use them. They stock a huge range of produce at low prices.
Their success also reflects changing lifestyles. People can drive to them at all hours. Young mums can park easily.
I think that the proposed Waitrose in Storrington would be a good thing. But we do need to be careful not to take unwise planning decisions about out-of-town stores that unnecessarily damage our high streets.
The last Conservative Government put in place planning rules on out-of-town retail development (known as PPG6) in order to prevent town centre decline. Local councils could reject proposals for new supermarkets and retail development outside towns due to lack of demand.
But the current Government has issued new planning guidance (PPS4) which abolishes the ‘needs test'.
The changes could mean a new wave of speculative out-of-town developments, worsening the problem of ‘ghost town Britain'.
Even the Government has admitted that their changes will lead to some overall increase in additional unplanned proposals outside town centres, which would have environmental implications.
These changes to planning rules should be reversed. In fact, as the Competition Commission has proposed, there should be an additional competition test to create more retail diversity within town centres.
I believe in the free market. But where there is too much power on one side there can be market failure - and then government has a responsibility to act.