Figures from HMRC show 36.7 million bottles were released for sale in the first six months of 2017 - down from 37.7 million in the same period last year.
The SWA says that the 2.6% fall is as a direct result of the decision to increase spirits duty in the Spring Budget by 3.9%, revealing that the increase now meant that tax makes up 80% of the cost of a bottle of Scotch.
The SWA has launched a ‘Drop The Dram Duty’ campaign in which it is urging the Chancellor to cut the duty on spirits.
Karen Betts, SWA chief executive, said: "Philip Hammond's damaging 3.9% spirits duty hike has hit UK demand for Scotch and seen less money going to the Treasury.
"The Chancellor should use his November Budget to Drop The Dram Duty and boost a great British success story.
"Cutting tax would send a strong signal that the Government believes in a world-famous UK manufacturing industry which supports 40,000 jobs and plays a key role in Scotland's economy."