Health Secretary Patricia Hewitt has defended the plans for a partial ban on smoking in public places in England.
Partial ban 'will save thousands of lives'
Critics and health experts have said plans to exempt private clubs and non-food pubs from the ban are bad for health and will prove "unworkable".
Ms Hewitt said "many of us would have liked to have gone further and faster" but stressed that even with exemptions 99% of workplaces would be smoke-free.
The Conservatives want MPs to have a free vote on the "untenable" plans.
Ms Hewitt is thought to favour a full ban on smoking in all enclosed public spaces, and proposed a wider ban which would only have exempted sealed staff-free "smoking rooms" in non-food pubs.
But those plans were abandoned after rows with Cabinet colleagues - rows which ended with agreement to return to the partial ban proposed in Labour's election manifesto, drawn up by ex-health secretary John Reid.
Those manifesto plans had been ditched earlier this month after a three month consultation period reportedly concluded they were "unworkable" and that many pubs would just stop serving food.
Ms Hewitt told BBC Radio 4's Today the plans had disadvantages, but said there were disadvantages with all the options.
She said: "The bill that I am introducing today is going to ban smoking in every office, in every factory, every shop, every restaurant, every public transport, virtually every enclosed public space and work space.
"This is an enormous step forward for public health... it is going to make it easier for people who want to give up smoking to do so... over time it will save thousands of lives."
MAIN ASPECTS OF BILL
Smoking - Legislation to ban smoking in workplaces to be outlined, although certain pubs and private members clubs will be exempt
Superbugs - A new hygiene code of conduct to be introduced for health providers to help reduce hospital infections
Shipman safeguards - Tighter management of controlled drugs after inquiry into the GPs' murders
Pharmacies - Reform of way chemists work and the role of staff
Asked about the Cabinet splits, she said: "There is total agreement on 99% of the policy. On the 1%, not only in government but I think across the country, there was real disagreement."
Ms Hewitt said she still believed that a complete ban on smoking in enclosed public places, as planned or coming into force in Scotland, Wales and Northern Ireland, was probably inevitable.
The bill includes a provision for the measures to be reviewed after three years.
She stressed there would be public consultation on how to protect staff in pubs where smoking will still be allowed - possibly giving a second chance for her plan to restrict smoking in exempted pubs to sealed "smoking rooms".
Anyone found in breach of the smoking ban would be issued with an on-the-spot fine of £50, Ms Hewitt later told MPs on the health select committee.
Asked about the plans, Labour MP David Taylor, chairman of the all-party group on smoking and health, told BBC Radio Five Live it was quite clear that the exemption for non-food pubs would make the new legislation "unworkable".
Shadow health secretary Andrew Lansley said: "The Government's plans are untenable. No-one except John Reid thinks they will work.
"The plan to ban smoking in pubs that serve food will do nothing to reduce health inequalities, as those pubs which don't serve food are often located in more deprived areas."
James Johnson, chairman of the British Medical Association, expressed his "utter disappointment" at the "wasted opportunity to protect the public's health".
Professor Alex Markham, chief executive of Cancer Research UK, said he was "utterly dismayed" at the plans.
The Health Bill also includes measures to tackle MRSA, new rules on managing controlled drugs, proposals to pave the way for reform of pharmacies, including new roles for pharmacy staff.