An online drinks offer intended for limited distribution has sent the e-commerce website belonging to off-licence chain, Threshers into meltdown.

The discount voucher, offering 40% off wine and champagne was supposed to have gone to suppliers and friends but turned up on the website of South African wine company Stormhoek, and has since been downloaded 800,000 times.

Threshers website has crashed under the strain and a company spokesperson is reported to have said: “It was never intended to get this big.” But the voucher has since appeared in blogs, emails and chatrooms.

The spokesperson admitted the company was holding its breath over the weekend to see if the offer could hit its profits.

Retailers have been using the viral marketing tactic, known as “secret sales”, by a number of High Street chains including Gap and New Look.