mystery meat, which has defied the best efforts of scientists to identify it, has been found in a lamb curry as part of an investigation into food fraud.

The discovery raises new questions about just what is going into the nation’s takeaways and processed foods.

A BBC documentary to be aired on BBC3 tonight sent samples of curries and kebabs bought from six outlets in London for laboratory tests.

The meat in a Beef in Black Bean Sauce dish turned out to contain high levels of chicken material including blood, while a burger contained no beef at all, other than blood and heart.

However, most alarming of all was a curry. A spokesman for the programme said: ‘Just when we thought things couldn't get any worse, the results came in for an Indian Lamb Curry.

‘It did contain meat, but that meat was not lamb, not pork, nor was it chicken or beef. Not horse, and not goat either.’

All of the many tests to date by the lab used by the programme have failed to identify exactly which animal was the source of the meat.

The revelation raises many grim possibilities. There is evidence from Spain, for example, of meat from dog carcasses being processed for use in pet food.

This is not the first time that a question mark has been put over the content of the take-out dishes eaten by millions of Britons every day.

Just last year, a survey of 20 lamb curries in the West Midlands found all had been bulked up with cheaper beef, pork and chicken.

Amazingly, four contained no lamb at all, rather the outlets used either beef or chicken which was hidden beneath a powerful and spicy sauce.

At the same time, a meat cutting plant in Wales has been accused of supplying horsemeat from an abattoir in Yorkshire to companies making kebabs and burgers for hundreds of independent take-aways.

The discovery of horsemeat in big brand products sold by supermarkets like Tesco and Asda, together with chains like Burger King and big brands from Birds Eye to Findus, has changed the nation’s shopping habits. The implication of take-out curries in food fraud could also hit the industry hard.

Horsemeat Banquet, BBC Three, March 27, 10pm.