Advising first-aiders to give the "kiss of life" is off-putting and unnecessary, say medics.
Chest compressions help pump blood round the body
Not only are bystanders less likely to help someone who has collapsed if they have to do mouth-to-mouth ventilation, many are unable to perform it properly.
Chest compressions alone are just as good if not better in most cases, a Japanese study in The Lancet shows.
They recommend resuscitation trainers revise their advice. But the British Heart Foundation disagrees.
The current advice is to give mouth-to-mouth ventilation unless you are unable, or are unwilling.
Studies show less than a third of people who collapse in public are helped by a bystander.
HOW TO GIVE CPR
Is the patient unresponsive? If so, shout for help
If they're not breathing normally, call 999
Then give 30 chest compressions at a rate of 100 times a minute
Next, give two rescue breaths, then 30 chest compressions...repeat
Source: Resuscitation Council (UK)
Surveys reveal many would-be first-aiders are put off by the idea of giving the kiss of life - for fear of catching an infectious disease, for example.
And when bystanders do assist, giving mouth-to-mouth can steal time from giving essential chest compressions.
Furthermore, if the patient has collapsed because of a heart rather than a lung problem they should already have enough oxygen in their body to keep them going without needing rescue breaths from a bystander.
Dr Ken Nagao and colleagues at the Surugadai Nihon University Hospital in Tokyo say in these circumstances it would be better for all parties to stick to giving chest compressions alone, which they called cardiac-only resuscitation.
Chest compressions 'key
They checked their theory by looking at the outcomes of more than 4,000 adult patients who had been helped by bystanders.
They found chest-compression-only resuscitation was the clear winner compared with conventional CPR (cardiopulmonary resuscitation, or mouth-to-mouth breathing together with chest compressions).
Colin Elding of the British Heart Foundation said a number of studies had shown it could be as effective as combined mouth-to-mouth ventilation and compression in many cases.
But he said it was right for CPR guidelines to still include mouth-to-mouth.
He added: "The current guidelines state, however, that for 'lay person' CPR, if the rescuer is unwilling or unable to give rescue breaths they should give chest compressions only and that these should be continuous at a rate of 100 per minute. The BHF believes this is sound advice.
"Cardiac arrests are a serious problem in the UK, which is why the BHF recently launched its Doubt Kills campaign, to encourage people experiencing potential heart attack symptoms to call 999."