Official figures show 36.7 million bottles were sold in the first six months of 2017, down from 37.7 million in the same period the previous year.
The 2.6 per cent drop in demand follows March Budget increase in spirits duty by 3.9 per cent, taking tax up to 80 per cent of the cost of a bottle of Scotch.
The Scotch Whisky Association has launched the Drop the Dram Duty campaign calling on Chancellor Philip Hammond to cut tax on spirits in the Budget next month.
The association said of an average bottle of Scotch sold at £12.77, more than £10 goes to the Treasury, comprised of £8.05 in excise duty and £2.13 in VAT.
The HM Revenue and Customs figures show the overall tax take from spirits has fallen since the March budget spring increase.
Spirits revenue dropped more than 7 per cent in the first financial quarter of 2017/18, down to £697 million compared to £751m in the same period from April to the end of June the previous year.
This reversed a 7 per cent increase in spirits revenue from the freeze on excise duty in 2016, which boosted the Treasury by £229 million.
The 2 per cent cut in spirits tax 2015 led to a 4 per cent rise in spirits revenue, a £124 million increase.
Karen Betts, Scotch Whisky Association chief executive, said: "Philip Hammond's damaging 3.9 per cent 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."
A Treasury spokeswoman said: "We recognise the importance of the Scotch Whisky industry.
"In the UK, tax on a bottle of Scotch is 90p lower now than it would have otherwise been, thanks to duty freezes and cuts introduced in the last three years."