The United Future party intends putting up an alternative to the proposed ban on smoking in restaurants, pubs, clubs and casinos.

Party leader Peter Dunne has drafted an amendment to a bill now before Parliament which would replace the ban with a clean air standard.

Smoking would be allowed in premises which installed filtration equipment to meet the standard; those that chose not to would have to be smokefree.

As it stands, the Smokefree Environments (Enhanced Protection) Amendment Bill will be enforced 12 months from the date it is passed, likely to be before the end of the year.

It covers all indoor workplaces as well as ships, trains and taxis.

Mr Dunne said that under his amendment a minimum air quality standard would be set by the Ministry of Health by February 2006 and regulations to enforce it would follow a year later.

"Ideology is irrelevant," he said. "This puts the onus on the bar owner, the restaurant owner, to make the decision whether to put the equipment in. So long as they meet the air standard, it doesn't matter what goes on. If they can't meet it, then they're smokefree."

Mr Dunne said an outright ban would hurt the hospitality sector.

"I don't think that in New Zealand, where the industry is pretty important to us, that it's a very bright path to go on."

The bill is not Government legislation. It is promoted by Labour MP Steve Chadwick, and some parties are allowing their MPs to cast conscience votes.

But Health Minister Annette King supports it and Labour MPs are expected to follow her lead.

New Zealand First and Act oppose it, and National's MPs will be free to choose.

Mr Dunne said his eight MPs would vote for the bill if the amendment was carried. He had not decided how the party would vote if it was not carried.

If all Labour's MPs vote for the bill the Government still needs another party's support to ensure it is passed, and that assurance will probably come from the Greens.