Many police forces are trying to raise awareness

The number of people who claim to have been sexually assaulted after drugs were put in their drinks rose to 1,000 this year, the Roofie Foundation said.

The group, which helps victims, said a media campaign should be run alongside the annual drink-drive messages.

Out of 30 police forces contacted by the BBC, two-thirds said they were running their own Christmas campaigns.

Many forces have been issuing leaflets and posters in attempts to raise awareness of the issue.

Pub and club-goers have been warned not to leave drinks unattended, and not to accept drinks from strangers.

Date-rape drugs include GHB (gamma hydroxybutyrate), valium, tamazepan and rohypnol.

Safe drinking practice: Do not leave a drink unattended If drinking from a bottle, keep your thumb over the top Take your drink with you to the lavatory Do not accept drinks from strangers

Most are clear, odourless and tasteless, so most people will be unaware if their drink has been tampered with.

Effects may include feeling unusually drunk very quickly, drowsiness and poor recall afterwards.

The Roofie Foundation - named after the street-name for date-rape drugs - begin compiling records seven years ago.

Since then, the number of people reporting assaults has steadily risen until it topped more than 1,000 this year.

There has been other alarming evidence from around the country about the scale of the problem.

One Swansea hospital doctor recently said he could see as many as 10 victims of so-called date rape drugs in one weekend.

Police posing as glass collectors in an Essex club found eight out of 200 drinks had been spiked.

And Cumbria Police said it received up to seven reports a month from people who believe their drinks may have been spiked.