Tony Blair admitted today that he used alcohol as a "prop" to escape from the pressures of being Prime Minister.

Mr Blair insisted that he was not an "excessively excessive" drinker and always believed he was "in control" of his alcohol intake.

But in his memoir, A Journey, he confessed that he was never sure whether his drinking was good or bad for him, adding: "You have to be honest: it's a drug, there's no getting away from it."

Mr Blair wrote: "By the standards of days gone by I was not even remotely a toper, and I couldn't do lunchtime drinking except on Christmas Day, but if you took the thing everyone always lies about - units per week - I was definitely at the outer limit.

"Stiff whisky or G&T before dinner, couple of glasses of wine or even half a bottle with it. So not excessively excessive. I had a limit. But I was aware that it had become a prop."

Mr Blair said he could "never work out" whether alcohol was good for him because it helped him relax, or bad because he could have been working instead of relaxing.

He came to the conclusion that the benefits of relaxation outweighed the cost to his work.

"I thought that escaping the pressure and relaxing was a vital part of keeping the job in proportion, a function rather like my holidays," he wrote.

But he added: "I was never sure. I believed I was in control of the alcohol. However, you have to be honest: it's a drug, there's no getting away from it."

Commenting on references to drink in the book, former home secretary Lord Reid told GMTV: "I've read the book... let me tell you what he says in the book - in about 500 pages he devotes three paragraphs to it.

"He wonders whether drinking one stiff gin and tonic and a couple of glasses of wine a night during dinner, was that a big step up?"

"Well, it might have been for Tony who didn't normally drink; where I come from, a gin and tonic, two glasses of wine, you wouldn't give that to a budgie.

"I speak with some authority on this. All I am saying is 'Don't believe the headline'."