And landlords who continually turn a blind eye to the practice will be putting their licence in jeopardy.

For many don't realise that pub doorways are also covered by the proposed smoking ban in Northern Ireland.

It comes into effect in April and includes all 'enclosed' public places as well as the workplace.

The ruling also extends to phone booths, bus shelters and sporting facilities that are either fully or substantially roofed.

But pub landlords are predicting that the doorway ban will spark a loss of goodwill from customers.

One leading Belfast publican said last night: "How do you tell an elderly regular that he, or she, has to leave the shelter of the doorway and go out into the sort of howling gales we've had recently?

"I've no doubt that in applying the letter of the law we will lose customers. Many people don't see entrance halls and doorways as part of the main pub.

"They are in for a shock come April because staff will be duty-bound to move them outside."

Hotels and restaurants will be faced with the same restrictions.

"It will be particularly difficult in the case of a funeral aftermath when those attending are already upset enough," one hotelier admitted.

There was overwhelming support for the implementation of a smoking ban in the province.

Grim statistics show that 800 people die every year from lung cancer.

But smokers lobby group Forest said: "To ban people smoking in doorways is unnecessarily punitive.

"We believe the law will have to show some commonsense and flexibility. "

A special hotline to report people who flout the no-smoking rules is expected to be introduced on the same day the ban comes into effect.