Diageo has been accused of damaging the “integrity and credibility” of Scotch whisky.

The spirits giant has come under fire for failing to change the name of its Cardhu brand - called after the distillery where it was first produced - even though it is no longer a single malt made exclusively at the distillery, but a combination of spirits sourced from different plants.

It has also been blasted for attempting to sidestep the issue by returning the distillery to its original name of Cardow, removing the link with the brand.

Diageo says depleted stocks left it with no choice but to turn Cardhu into a premium blend and that it had replaced the term ‘single’ with ‘pure’ on the bottle. Communications director in Scotland, Peter Smith, said: “It isn’t written in neon lights, but the label does state that it’s a ‘pure’ malt. Research shows (with this brand)that the concept of provenance is unimportant.”

Rivals fear the move could open the way for companies to name brands after distilleries that have no role in their production, giving drinkers’ a false guarantee of provenance.

John Grant, director of rival malt producer Glenfarclas, said: “Diageo’s use of the Cardhu name makes a mockery of distillery names indicating a bottle’s content. It’s playing with words (by renaming the distillery).”

The Scotch Whisky Association said it was in talks with Diageo to protect the industry’s reputation.