Such a legacy from a government minister, once given responsibility for the international war on drugs, may provide Tony Blair with a rueful reminder of the controversy she sparked with her admission while in office that she had smoked cannabis at university.

Mowlam had been working on the manuscript for much of this year with Jon Norton, her husband, and had almost finished it. Last Thursday, the day before her death, Norton told their publisher, Polity, that he will complete it by the end of the year.

“We are very proud to publish this important book. I am delighted Jon has decided he does want to finish it,” said Louise Knight, Polity’s editorial director. She said the working title of the book was Legalise Drugs and added: “They are putting forward an argument for regulation, not just for a free-for-all. It is based on Mo’s extensive experience.”

Before her death, Mowlam had floated the idea of legalising drugs at a series of informal speaking engagements entitled Audiences with Mo Mowlam. She became convinced that it could be a popular idea if properly presented.

She attracted controversy when she confessed to smoking cannabis while working as a social anthropology student at Durham University in the late 1960s. “I tried marijuana, didn’t like it particularly and, unlike President Clinton, I did inhale,” she said. “But it wasn’t part of my life.”

She later argued for the sale of cannabis to be taxed and regulated in the same way as alcohol and tobacco.

Mowlam formed her view that addictive drugs should be sold at regulated outlets as a result of her experience as a minister in the Cabinet Office between 1999 and 2001.

However, on leaving office she became convinced that a more radical approach was needed and advocated that legalising narcotics was the most practical means of destroying the illegal market.

Her book is also expected to be highly critical of the American-led war against drugs and of George W Bush’s policies on the issue.

Her posthumous strike at Anglo-American drugs policy is likely to sit uncomfortably with Blair, who broke off his Caribbean holiday to praise her as “one of the shrewdest political minds I ever encountered” who “could read a situation and analyse and assess it as fast as anyone”. Blair is not expected to attend Mowlam’s funeral, which is described as private, but he will be going to a more public memorial service later this year.

Mowlam died as a result of the side-effects of radiotherapy she received for her brain tumour eight years ago, her husband reveals today. The treatment caused brain damage leading to a loss of balance and a form of dementia.

The couple were told last month after the effects became worse. “It was the first time that the doctors explained to us the effects of the radiotherapy,” Norton tells The Mail on Sunday. “It was a shock but at least we felt we finally understood what was going on.

“It had not been fully explained to us at the time, but we had had a stark choice: radiotherapy or death. At least she had an extra eight years.”

In Northern Ireland, where Mowlam is credited with helping to put together the Good Friday peace agreement, there are calls for a permanent tribute, including a memorial park in the grounds of Stormont.

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