Far-reaching restrictions on smoking in pubs and clubs in England will be agreed by MPs tonight, with the only likely exemption to be for private members' clubs.
In a series of free votes on the government's health bill, the Commons will decide whether to impose blanket ban from 2007, or allow an exemption for private members' clubs, or a bigger exemption for pubs and clubs not serving food.
The votes are expected around 9pm, with all three parties allowing a free vote.
The health secretary, Patricia Hewitt, will vote for a complete ban, a spokesman said tonight.
He said Ms Hewitt had been swayed by arguments in this afternoon's Commons debate where the health secretary predicted that the public work spaces ban would help 600,000 smokers quit the habit.
Her deputy, the public health minister Caroline Flint, has indicated she will also vote for a total ban.
Ms Hewitt was accused by her Tory shadow, Andrew Lansley, of presiding over a "shambles", after the government dropped its initial compromise option (and manifesto pledge) to allow non-food serving pubs to continue to allow smoking.
The Tory leader, David Cameron, will miss the vote, as his third child, a son, was born today, and he is now on paternity leave.
Whatever the precise result, the bill when it comes into force will impose far severer restrictions on smoking in public places than currently exist. Only private homes, care homes, hospitals, prisons and hotel bedrooms will be permitted exemptions.
Whilst cancer research groups have been lobbying MPs all day for a full ban, pub groups also fear that an exemption for private members' clubs will see a growth in their business at the expense of traditional pubs.
With the Scottish parliament having already opted for a total ban starting in April, and the Welsh assembly indicating it will implement a total ban once the legislation is passed at Westminster, some MPs argued it was unfair for Scottish and Welsh MPs to vote on a matter pertaining only to England.
Some Tories argued that a ban could result in an increase in smoking in domestic homes - exposing more children to secondhand smoke.
The compromise option hammered out before the election - a ban excluding pubs which do not serve food - is thought to be the least likely to succeed, as critics fear it will exacerbate existing health divides between rich and poor, and jeopardise the health of significant numbers of pub workers.
As it is a free vote, rejection of this option will not technically count as a government defeat.
Nevertheless, the vote remains a sensitive issue for ministers in a week of crucial Commons votes, after last night's scraping through of the ID cards bill, and a big vote tomorrow on the creation of a "glorification of terrorism" offence.
Health campaigners have warned that anything short a total ban would heighten health inequalities, while many pubs are opposed on competition grounds to an exemption for private members' clubs.
Meanwhile, some ministers fear that an outright ban will alienate many core Labour supporters.
Labour MP John Grogan, who chairs the all-party beer group, urged MPs to go for a complete ban.
He said allowing smoking to continue in private members' clubs only would be unworkable. He said pubs would close because they would lose customers to private clubs. And he warned the clubs could face legal action from their staff.
"All other laws apply across licensed premises," the Selby MP told the BBC Radio 4 Today programme.
"Noone would suggest the minimum wage or health and safety legislation should not apply to clubs."
Mark Hastings, from the British Beer and Pub Association, urged MPs to extend the smoking ban to private members' clubs as well as pubs.
He said a ban in pubs alone would present landlords with a "enormous competitive challenge".
"The pubs will suffer as a result. Our lobby is around trying to persuade MPs to just go that extra step and to create one law for all.
"If we do have laws in this country then we should all be equal under them."
