Introducing a smoking ban in England would help smokers to kick the habit, health experts told MPs.
Smoking is linked to premature death
But government officials and health professionals told the Health Committee the main reason for a ban was to protect people from passive smoking.
The cross-party group of MPs has launched an inquiry into smoking in public after ministers unveiled a plan last year to partially ban smoking.
Industry representatives said there was insufficient evidence for a ban.
Dr Fiona Adshead, deputy chief medical officer, told the Thursday hearing that the plan to ban smoking in all workplaces, with the exception of private members clubs and pubs which do not serve food, was being driven by the desire to protect people from second-hand smoke.
But she also argued it would have the added effect of "encouraging people to give up".
The committee was told that bans in other countries had led to a 4% fall in tobacco sales and that could be repeated in England.
But Dr Adshead also came under attack for the decision in last November's Public Health White Paper not to introduce a full ban.
Labour MP Charlotte Atkins said the partial ban could worsen health inequalities as pubs in more deprived areas tended to be the ones which were exempt.
Dr Adshead said that was something that politicians would have to consider when the smoking ban bill was published.
It is uncertain when the bill will be revealed to parliament as the proposed measures are being discussed in cabinet after the public consultation ended recently.
There has been some suggestions ministers may now decide to go for a full ban or scrap the exemptions but allow enclosed smoking rooms.
Health professionals addressing the committee said nothing but a full ban would be good enough to help prevent heart disease, lung cancer, strokes and chronic bronchitis.
Professor Carol Black, president of the Royal College of Physicians, said: "There was no excuse for a partial restriction."
She said it would be impossible to confine smoke solely to smoking rooms and, therefore, staff and non-smokers would not be protected.
And Dr Richard Edwards, a lecturer in public health at the University of Manchester, countered claims ventilation could be used, saying it had "no significant effect".
But industry representatives once again said a ban was not necessary.
Christine Mohrmann, head of UK corporate affairs at Philip Morris, said measures such as ventilation and warnings in pubs about smoking should be adopted instead.
And Dr Steve Stotesbury, chief scientist at Imperial Tobacco, added voluntary agreements were making progress with an increasing number of non-smoking pubs and greater segregation in recent years.
He also added "the scientific evidence as a whole" was insufficient to warrant a ban.
Labour MP Howard Stoate replied the tobacco industry did not have "a good record" on voluntary agreements, citing the need to introduce legislation to curb advertising.