National press ads promote the offer, which runs from July 5 to 22 in branches of Threshers and Thresher Wine Shops.
The deal applies to any of the still wines in the retailer’s range, but cannot be combined with three-for-two or other offers.
Tesco is running a similar deal – 30 per cent off six bottles of selected wines and Champagnes – until July 8.
In December last year, Thresher enjoyed a 60 per cent sales boost after thousands of punters used a discount voucher published on the internet. It removed Champagne and sparkling wine from three-for-two in May, instead offering a 20 per cent off three bottles deal.
Thresher has also confirmed its first national English wine listing – Chapel Down Brut. The wine – which won a silver medal at this year's International Wine Challenge – will be stocked at 400 branches of Threshers and Wine Rack.