The average 25-year-old man would drink around 23 units a week - the equivalent of about 10 pints - according to the study.

Alcohol is the number one 'date rape' drug in Ireland, according to experts.

While there are cases of sexual predators using drugs such as Rohypnol to incapacitate vulnerable women, secretly giving 'double shots' of alcohol is far more common.

Cliona Sadlier, of Rape Crisis Network Ireland, has warned that a popular tactic employed in cases of serious sexual assault is to surreptitiously strengthen the drink of someone who is already voluntarily consuming alcohol.

"Drink-spiking includes giving a person a double or a triple shot, when they think they've got a single," she said.

"The culture of permissiveness around alcohol - as well as a belief by some victims that they may subsequently not get a sympathetic hearing - cannot be ignored."

She said women in these situations can feel a strong sense of shame because they were so intoxicated. "If they make a complaint they fear some people will say 'sure they were asking for it'.

"There's often a concern they simply won't be believed by gardaí, and that their case won't be investigated in the same way as if they were sober at the time of the assault. "But people need to realise that rape is rape - whether the victim is drunk or sober."

Around 80pc of rape cases occur when women have consumed alcohol.

Irish Independent