The campaign warns revellers to watch their drinks

Thames Valley Police have launched the new campaign after receiving up to two reports a week from people whose drinks in bars or clubs tasted stronger or weaker than usual, or had an abnormal effect on them.

Posters telling clubbers: "Don't let spike strike" are now being put up across the Reading and Wokingham areas.

The force says spiking a drink does not just mean adding a drug, it can also mean stronger alcohol being added without the drinker's knowledge.

Soft drinks can also be targeted, they said.

Thames Valley Police crime reduction adviser, John McNicholas, said: "Tens of thousands of people visit this police area in the evening to enjoy themselves in the hundreds of clubs, pubs, bars and restaurants.

"Our message to anyone having a drink, even at a private party, is not to leave it unattended."