WHISKY traditionalists are fighting a rearguard action against plans to shake up production of Scotland’s national beverage – with suggestions including maturing malts in tequila casks, using chocolate malt in the mash and even marketing low-alcohol “infusions” under big brand names.

Diageo, the world’s single biggest producer, has confirmed the existence of documents exploring ways to create more innovative products, as Scotch whisky faces increasing pressure on its market dominance.

Scotland exports around £4 billion worth of whisky annually, but while Scotch used to make up 60 per cent of the world market, that has declined to less than 50 per cent amid intense competition. Uncertainty over how Brexit may affect the £1.2 bn of exports that go to Europe is adding to the concern.

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Diageo’s proposals, first unveiled by the Wall Street Journal, come from a secret task force seeking to change the laws and rules which govern how whisky is made, but are likely to face resistance from the Scotch Whisky Association (SWA). The trade organisation oversees the rules about how whisky is made helping produce guidelines to police innovations and clarify ambiguities.

Suggestions put forward in the documents prepared by the task force include ageing and finishing the spirit in old tequila barrels – rather than the traditional oak casks previously used only for wine, sherry or port.

Another suggestion is a new category of blended whisky, to be sold under existing brands, but made to be flavoured or lower in alcohol content. One document warns of “overreach” on the part of the SWA.

However the rules governing the production of Scotch dictate that it has to be distilled in Scotland from water and barley, has to be aged for at least three years in oak casks and must be at least 40 per cent alcohol.

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Diageo insists it is “unwavering” in its commitment to the integrity, history and tradition of Scotch. But a spokeswoman added: “As champions of Scotch, we are always looking at ways to innovate to both protect and secure the future success of the category.

“In doing so, we work with the Scotch Whisky Association on a range of ideas that seek to strike a balance between tradition and innovation, in a way that ensures consumers get the great products they want.”

Others are also seeking a loosening of the rules, to allow a more varied range of products. They point to the success of craft breweries and craft gin in seeking a wider customer base by offering more unusual drinks.

Paul Miller, of Eden Mill Gin abandoned plans to incorporate chocolate malt in the mash used to make his new Scotch, after the SWA told him it might “lead to the production of a spirit which differs from traditional Scotch Whisky.”

Mr Miller, whose first single malt Scotch will be produced later this year, says he too understands the need to protect the uniqueness of Scotch Whisky.

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He added: “I respect the job the SWA does in upholding the value of Scotch.” But he added: “It it has always been a pioneering industry. The challenge is to uphold the Scotch Whisky Act, while not restricting creativity.”

Mr Miller thinks the act – which sets out in detail how Scotch should be produced – should be subject to periodic review.

“We have the best educational institution for brewers and distillers in the world at Heriot Watt university. It would be a real shame for these people not to have an opportunity to demonstrate their creativity.”

There is also an economic imperative, to allow diversification while not losing the uniqueness of Scotch whisky, he said. “To ensure there is not a limitation on the potential growth of the business we need to manage that tension rather than ignoring it. If we are not prepared to innovate, we risk becoming obsolete.”

Mr Miller also called for a relaxation of the rule which prevents distilleries from being identified in the marketing of blended whisky. “We need that transparency. If we use our creativity to produce a blended whisky we ought to be allowed to attach our credible name to it.”

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A spokesman for the SWA said: “Scotch Whisky is a product renowned for its quality, craft and heritage. The regulations which govern the production of Scotch Whisky are the solid foundation on which the industry’s success is built, generating over £4bn in exports to almost 200 market worldwide in 2016.

“The SWA regularly engages with our membership on a broad range of ideas to ensure that the category is well-placed to grow in an increasingly competitive global market place.”