Five pub companies yesterday announced smoking restrictions as part of a campaign to head off a total government-imposed ban.

By the end of next year drinkers will not be allowed to smoke at the bar of the 22,000 premises run by Mitchells & Butlers, Scottish and Newcastle Pub Enterprises, the Spirit Group, the Punch Pub Company and Enterprise Inns.

Within five years 80% of the trading space at those pubs and bars - which make up around a third of all premises in the UK - will be no-smoking areas.

The anti-smoking campaign group Ash attacked the plans as inadequate, claiming it was impossible to separate smoking and non-smoking areas because smoke drifted.

Ash expressed concern that if the move - which was welcomed by the government - staved off legislation it would be more difficult to frame legislation for other workplaces.

Others within the hospitality industry were frustrated that the companies were going it alone when they were trying to hammer out a voluntary charter with the government. The pro-smoking group Forest called the moves "over the top".

There has been concern among many pub companies that the government will ban smoking in enclosed public places. Most landlords prefer to offer customers a choice.

In a statement the five companies said the programme would "transform pubs into primarily no-smoking venues".

The chief executive of Mitchells & Butlers, Tim Clarke, said: "The policy is the result of careful consideration of the needs of both smokers and non-smokers and is the best way to provide choice for all our customers."

But the companies conceded that the move was about profits, pointing out that the ban on smoking in pubs in Ireland had led to a 15% fall in trade.

The issue is likely to form part of a white paper being drawn up by the Department of Health.