IT is Scotland’s national drink that adds £5billion annually to the country’s economy and is worth more than £4bn in exports. But concerns have been raised for the whisky industry over the impact of a post-Brexit trade deal with the United States.

US trade groups want any deal between the UK and America to drop EU rules relating to the ageing of whisky – which would mean US manufacturers could promote their rival, younger products as “whiskey”, the spirit made by non-Scottish producers that is spelled differently.

Transparency campaigners claim discussions between the two countries over what can and cannot be included in a potential trade deal are being conducted in secrecy.

Last December, Greenpeace’s Unearthed investigations unit reported the UK and the office of the US trade representative had signed an agreement that data relating to the talks should be considered “sensitive” or “confidential”.

But some key issues can be gleaned from the annual barriers to trade analysis, prepared by the Office of the United States Trade Representative.

The document discusses the current EU requirement that a product labelled as whisky or whiskey must be aged for a minimum of three years as a quality requirement.

It reads: “The US has a long history of quality whiskey production, particularly by micro-distillers, which has not entailed minimum ageing requirements, and views a mandatory three-year ageing requirement for whiskey as unwarranted. Recent advances in barrel technology enable US micro-distillers to reduce the ageing time for whiskey while producing a product commensurate in quality.”

Nick Dearden, director of Global Justice Now, said: “We’re always told international trade deals will help us sell more whisky, but this information from the US trade representative shows a trade deal with the US could be a threat to this famous drink.

“ The US government doesn’t like our food standards, and repeatedly tells us abandoning these standards for imports is essential if it is going to sign a deal. That means allowing food like chlorine-washed chicken and hormone-fed beef into our markets. But it could also mean changing the standard on the production of whisky and allowing iconic products like Stilton to be made in the US.”

A Scotch Whisky Association spokeswoman said it would campaign for EU food standards to be applied to any trade deal with the US.