A study by a pharmaceutical company has found that one in three smokers ruin another person's attempt to quit.
The reasons to wreck other people's quitting attempts include jealousy, guilt about their own habit and wanting a smoking "buddy".
Pfizer collected data from 6,300 current and former smokers and found that 31 per cent of smokers admit being saboteurs. The study also found that 72 per cent of smokers who have tried to quit think someone has tried to ruin their attempts.
On average, smokers said they tried to kick the habit at least three times. One in five said they had tried five times or more.
"Beating a smoking addiction is hard enough without the negative influence of others around you casting doubt," the Daily Telegraph quoted London-based GP Sarah Jarvis as saying.
"I want those who are motivated to give up smoking to be aware that they don't have to go it alone and that there is support available.
"Even a brief conversation with their healthcare professional ... can increase their chances of success by up to four times, compared with going cold turkey," she added.