One-third of meat in sandwiches bought from British shops is unidentifiable, according to a Channel 4 documentary.
The grim discovery was made by researchers in Channel 4's The Truth About Your Sandwich.
Journalist Helen Skelton spoke to a researcher, named Mark, who said it is becoming increasingly difficult to find out where the meat in sandwiches comes from.
Mark said his team spent a "fair old period of time" looking at sandwich packaging, carrying out Internet research and talking to retailers.
They were unable to find out where the meat had originated from for 33 per cent of sandwiches.
Mark said: "We also spoke to those retailers and they said 'well we know where the meat is coming from', but what does that mean to the consumer?
"I think it's a concern because if the retailers aren't even telling you which country it comes from, they certainly aren't telling you how it is produced, where the animals are living or if its organic."
It was later revealed in the programme that the average sandwich contains 25 different ingredients.
The documentary is set to see Ms Skelton investigate hygiene measures at a major sandwich chain, unreliable nutritional advice and dirty conditions at other major production plants.
