The health secretary, Patricia Hewitt, tonight held out an olive branch to critics of the government's partial ban on smoking in pubs, hinting that the prohibition could apply to all pubs by 2010.
Defending the bill to Labour backbenchers, many of whom would like to see a complete ban, Ms Hewitt pointed out a clause allowing for a three-year review of the ban, which could then trigger an end of the proposed exemptions for pubs not serving food and private members' clubs.
She tacitly admitted that the current exemptions had caused a long-suspected row in the cabinet, telling MPs: "Hand on my heart, we had a debate within government on how best to implement our manifesto promises."
She was speaking after the Liberal Democrats demanded to know whether she had disagreed with her predecessor as health secretary, Dr John Reid, on the exemptions, which will apply in neither Scotland nor Wales.
The row came as MPs got their first chance to debate the health bill, which will ban smoking in all public workspaces and pubs (bar those serving food) from the summer 2007.
Ms Hewitt called the move a "landmark in the protection of public health" and accused the Conservatives of having an "irresponsibly laissez-faire" attitude after one Tory MP attacked the bill as "nanny-state intervention."
Only a small rebellion, if any, is expected at this stage of the bill, as rebels are intending to table amendments at a later stage. The health bill also includes measures that they do not want to jeopardise to combat the hospital bug MSRA.
Ms Hewitt appeared to offer a middle way towards a full ban when she told critics suggesting a "sunset clause" on the exemptions for pubs not serving food that the 2007 introduction would see a three-year monitoring programme and a review. If that review suggested a complete ban, she said, it could be brought in without further primary legislation.
Several Labour critics of the bill, such as Liverpool's Louise Ellmann, had complained that allowing workers in private members' clubs and pubs without food to be exposed to smoke would create "two classes of workers".
Others feared that such pubs would be predominantly in deprived areas, exacerbating the health divide between rich and poor.
Earlier today the former health secretary Frank Dobson attacked the bill as "half- hearted and half-baked" for allowing certain classes of pubs to be exempt.
Ireland has already implemented a complete ban on smoking in pubs, with one due in Scotland next year. The Welsh Assembly, which is covered by the current bill, has indicated that it will not allow the exemptions in Wales.
In a stunt to publicise the dilemma some pubs will face between allowing smoking or serving food, health charities today organised a tug-of-war outside parliament between volunteers dressed as a sandwich and two cigarettes.
Cancer UK and Asthma UK organised the "fags versus food" event after concerns that pubs in deprived areas may close their kitchens in order to keep smoking customers.
More than 80 MPs, including 50 Labour backbenchers, have signed a parliamentary motion calling for a complete ban of the kind that will come into force in Scotland next spring, outlawing tobacco in all restaurants, bars, pubs and public buildings.
Liberal Democrat MP Paul Burstow claimed that a partial ban would cause the death of around 200 bar workers. Ms Hewitt insisted the bill - which outlaws smoking in all enclosed public spaces - will increase the percentage of workers in smoke-free environments from 51% of the workforce to 99%.
Private dwellings, prisons, mental health homes and hotel bedrooms are also exempt from the provisions of the bill.
