Oxfordshire health chiefs have warned that smokers must be determined to quit if they want their GPs to prescribe a new wonder drug to help them conquer their habit, writes Victoria Owen.

Although the health authority has cleared the way for family doctors to give out Zyban, it claims it would cost 4m if every smoker asked for the tablets. While smoking is the single biggest preventable cause of serious disease in the UK, it will cost 85 to help every would-be quitter many of whom may not be fully committed and start their habit again.

And because the health authority has not set aside special money for Zyban, unrestricted prescriptions could lead to cuts in other important drugs.

In an effort to curb the spending, public health workers have listed conditions which patients must abide by before they can receive the nine-week treatment. Anyone who wants the drug must prove that they have already tried to give up cigarettes using nicotine replacement therapy, like patches or gum.

And smokers must also undergo intensive counselling throughout the treatment and afterwards.

Dr Tom Jones, of Oxfordshire Health Authority, said many people could become angry if their doctors decided they would not benefit from Zyban.

He said: "We do need to make sure it is being used to its best advantage. Some people may start smoking again and that would be a waste." The health authority has already started ploughing 150,000 into training up special smoking cessation workers in every county GP surgery.

During tests, 18 per cent of people managed to stop smoking for a year after taking the tablets.

But the drug does have side effects, including constipation and sleeplessness.