The year-long investigation in the UK and America will include interviews with people who claim they have been drugged and sexually attacked.

DI Peter Sturman explains how the research will work

A major area of investigation will be the drug Rohypnol, implicated in so-called "date rape" attacks on both sides of the Atlantic.

One of the Metropolitan police officers in charge of the study, Inspector Peter Sturman, said: "Over the last two years there has been growing public concern about possible use of drugs in order to commit rape and other sexual offences.

"We share these concerns and this new study aims to establish more fully the nature and scale of any drug mis-use of this kind.

"We are approaching this issue with an open mind."

He said the researchers would be speaking to people who believe they may have been the victims of "drug crime" and organisations who could contribute.

Rohyphnol (Flunitrazepam) is a colorless, odorless, tasteless drug that causes sedation or euphoria in approximately 15 minutes.

The drug is from the same family as Valium, but is approximately 10 times more potent. It is prescribed mainly for the short-term treatment of sleep disorders

People under the influence seem to be awake and functioning, but may not remember what they did some of the time they were active.

They become extremely relaxed and can lose bodily control, maybe even stop breathing. They appear drunk.