Israeli researchers have found a way to detect when drinks have been spiked with date rape drugs.

The research, carried out by two scientists at Tel Aviv University, involves a sensor which can indicate the presence of drugs including ketamine and rohypnol.

The drugs most commonly used to spike drinks are tasteless and don't tend to alter the colour of the liquid, making it difficult for potential victims to notice.

However when a drink is spiked it does change how it appears when in contact with a ray of light. In practical terms, the technology would mean that if a sensor were dipped into a drink and detected a drug, it could emit a noise or flash of light to alert the person to a problem.

Fernando Patolsky and Michael Ioffe tested their idea on a selection of different cocktails and in every case the drugged drinks were identified.

Although the technology is only in the early stages of development, the pair hope it could be for sale within 18 months.

The ultimate aim would be to market it as a small disposable test which could be carried around in handbags. "Maybe it would send a signal to your cell phone because you might want to be discreet about it," said Mr Ioffe.

He added: "We have some very, very optimistic preliminary results. All we need is money."