The impact the major retailers are having on British farmers and food producers by slashing prices in a fight for market dominance is being explored in a new TV documentary.

The Panorama Special – Supermarkets: What price cheap food? – will chart the expansion of Tesco, Sainsbury’s, Asda and Morrisons and examine the true cost of our cheap food.

The programme, due to be aired at 9pm on BBC1 on Wednesday (22 December), will ask how supermarkets can expand while they slash food prices in the middle of a global recession.

It claims that in recent years, supermarkets have moved to buying globally as more and more British food producers cannot keep up with their demands for lower prices.

But by shifting their focus outside Britain, critics claim they have destabilised Britain’s food infrastructure and put many farmers, milk producers and fishermen out of business.

In the Panorama Special, reporter Paul Kenyon looks behind the cellophane wrappers and buy-one-get-one-free’s.

According to the BBC website, Panorama has also “pieced together the location of every new store currently being planned and built”.

Their findings include supermarkets in churches, Tesco-financed police stations, and Asda-financed clinics. The programme also examine whether “Made in Britain” always means what is says.

David Handley, a Monmouth dairy farmer and chairman of the Farmers for Action lobby group, said he had been interviewed extensively for the programme.

Supermarket price wars and the rise of BOGOF have had a “disastrous impact” on traditional British farming, he said.

“The dairy industry has gone from 24,000 producers to 12,500, and it can all be traced back to the 1990s, when Tesco and Asda started to launch BOGOFs,” he added.

“British dairy farmers are not getting a fare share of the market returns. The economics do not stack up and many traditional family farms cannot continue in the present climate.”