Shaun Woodward, the Health Minister in the province, will make the announcement after months of consultation and pressure from those seeking a total ban and those wanting a partial one.

The Northern Ireland announcement comes as the Cabinet in London is still deciding how to proceed in England and Wales.

However, it is increasingly likely that the Government will drop plans for a partial ban exempting pubs and bars which do not serve food, opting instead for a uniform nationwide ban.

A consultation exercise concluded that the partial ban would be unworkable and unenforceable.

Mr Woodward is expected to follow the path of the Irish Republic, which introduced a total ban on smoking in the workplace in March 2004.

The minister — himself an ex-smoker — recently visited Dublin and New York to assess how both cities have administered their bans.

Over the summer he revealed the results of a public consultation in Northern Ireland which showed 91 per cent of respondents in favour of a total ban.

A ban in all Government departments came into force at the start of this year.

However, the legislation to be announced this week will take until April 2007 to come into effect, a year after that already announced for Scotland.

The Ulster Cancer Foundation said that the minister must not take the soft option of a partial ban.

“Shaun Woodward has been given a golden opportunity to drastically improve the health of the people of Northern Ireland,” Gerry McElwee, the head of cancer prevention at the foundation, said.

But Nicola Carruthers, chief executive of the Federation of the Retail Licensed Trade, Northern Ireland, said that she was making no predictions about what the minister would announce.

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