The Department of Health has denied that guidelines on responsible drinking were "plucked out of thin air".
It is recommended that men should drink no more than 21 units of alcohol per week, and women should drink no more than 14 units.
But Richard Smith, a member of the Royal College of Physicians working party that produced the safe alcohol limits back in 1987, said the thresholds were prompted by "a feeling that you had to say something".
He added: "They were not based on any firm evidence at all. It was a sort of intelligent guess by a committee."
However, a Department of Health spokesman said: "Individual tolerance to alcohol will vary.
"The current guidelines indicate the amount of alcohol which if not exceeded too often, are unlikely to cause health damage. Some people will drink more than this and not experience problems, but some will.
"Measuring in units and providing recommended daily units for consumption are the only way that people who drink alcohol can evaluate how much they are drinking.
"Most countries now measure alcohol in units and provide guidance on these, and although the advice they give may vary, the overall messages are the same."