Pubs are facing a crackdown on counterfeit spirits over Christmas.
Trading Standards Officers across the UK are focusing on the party season to catch out the minority of rogue licensees who switch branded spirits for cheaper varieties.
Customers are also being encouraged to report pubs where cheap spirits are being sold as premium brands.
The International Federation of Spirits Producers (IFSP) has issued local authorities with enough "dipstick test kits" to check over 100,000 spirit samples over the next few weeks.
The IFSP estimates that tipping, as the practice is often called, is generally in decline as the risk of detection increases.
However, in past years it has increased over the Christmas trading period, when spirits sales peak and many customers may be too full of festive cheer to spot an inferior product.
The dipstick authenticity kits can quickly and easily check any spirit being served across the bar. Philip Weston, a senior trading standards officer based in London said: "These authenticity kits are quick and easy to use so we can test many more premises. This activity, plus naming and shaming, in local press has reduced the instances of tipping.
"But we will continue our activities until every measure served over the bar is the genuine product."
Consumers are being urged to get in on the act via a press campaign. Philip Scatchard of the IFSP said: "The vast majority of licensees are not involved in this kind of illegal activity but there are always a few bad apples and they need to be caught and prosecuted."