The NFU leader launched Farming Counts with figures showing that out of an average shopping basket costing £37 the farmer only receives £11 - just 30%.
To make his point Gill will be setting up a stall in the centre of London selling fresh produce at factory gate prices.
He said: “It is shocking that farmers get so little of the final price of food. Crops and livestock are tended and nurtured by farmers for many months or even years. That investment and care justifies more reward.
“This enormous price discrepancy shows clearly why farmers are having such a difficult time, with many not even recouping the cost of production.”
The Farming Counts campaign will be rolled out across the country with a series of events over the next few weeks focusing on each sector of farming.