SCOTTISH farming leaders have been left "devastated" by the horse-meat scandal which risks tarnishing the industry's hard-won reputation.

The National Farmers' Union (NFU) Scotland has warned that the country's livestock farmers are becoming increasingly frustrated by the deepening crisis, which is in danger of damaging their livelihoods.

Yesterday it called on the Food Standards Agency (FSA) and the Scottish Government to get across to the public that Scotch meat standards remain among the highest in the world.

The union, which represents 9000 farmers, crofters, growers and others across the country, said it was determined "catastrophic failures" in parts of the food chain around labelling, traceability and sourcing of meat "will not derail the huge amount of time and effort gone into building Scotland's reputation for quality red meat".

Labour MP Tom Watson has claimed Findus beef lasagne, some of which contained up to 100% horse meat, may have been contaminated since the summer.

Aldi said its range of Today's Special frozen beef lasagne and Today's Special frozen spaghetti bolognese from the same French supplier, Comigel, were found to contain between 30% and 100% horse meat.

The FSA has ordered firms to carry out tests on all processed beef foods amid claims by the Trading Standards Institute that the findings suggest "deliberate fraudulent activity".

NFU Scotland president Nigel Miller said: "We are pretty devastated by what has emerged. It's a real blow to us. The ongoing scandal on horse meat is becoming increasingly frustrating for Scottish farmers who believe their hard work and reputation for quality is being undermined by potential illegality in some supply chains, wildly inaccurate labelling of processed products and a developing mistrust within the food supply chain.

"It would be helpful if the FSA and the Scottish Government made a statement laying down where they think the risks are and spell out the controls and monitoring going on. It would also be helpful if they gave assurances about the products they can guarantee under the present system."

The Scotch beef and lamb export market is worth an estimated £116 million, with both products attracting an EU protected status, meaning only meat shown to have been reared and produced in Scotland can carry the Scotch tag.

Mr Miller added that Scottish farmers comply with "robust identification and traceability measures, stringent farm-assurance programmes and are subject to very high levels of inspection".

He said: "The Scotch label means the animal has been born, bred, reared, slaughtered and processed in Scotland with every step subject to assurance and audit."

Mr Watson revealed the Findus products may have been contaminated since August 1. He produced a letter sent by Findus, admitting the supplier had possible problems with raw materials which were likely not to conform and "consequently the labelling on finished products is incorrect".

Scotland Yard confirmed officers had met the FSA over the scandal, but there is no official inquiry yet.

Food Minister David Heath urged people not to throw out frozen meat products and said they should continue shopping for meat. He added: "The advice is to carry on with normal shopping habits."

Environment Secretary Owen Paterson will today meet suppliers and heads of food retailers to discuss the crisis. He said he had "great confidence" in the industry but urged consumers to return the affected lasagnes to retailers. "It is wholly improper the public are presented with a product marked beef when it contains a significant amount of horse," he said.

Prime Minister David Cameron said the situation was "completely unacceptable", adding it was not about food safety but accurate food labelling, and the industry would have to work hard to restore confidence. He said: "People will be very angry to find out they have been eating horse when they thought they were eating beef."