The promotion launched today (Nov 19) and runs until Dec 2, and canít be used at the same time as the chainís existing three-for-two offer or other discounts. Some shops, such as those in mainline railway stations, are not included in the offer.
Thresher has run the same promotion for the past two years, and seen festive sales surges as a result.
In 2006, customers who thought the discount had been sent to them by mistake rushed to take advantage of it, giving the chain a 60% sales boost.
Last year shop managers said the promotion was just as popular, with many seeing a big uplift in Champagne sales.
This yearís promotion, available at thedreamoffer.com, has gained publicity on savings tips website moneysavingexpert.com, and has already gone viral, with consumers sending the link out to friends and contacts.