The Liberal Democrats have been hit by fresh allegations about the scale of Charles Kennedy's alcoholism during and before his leadership.
The book is being published on the eve of the Lib Dem conference
A new biography of Mr Kennedy, serialised in the Times, claims he was suffering from a drink problem even before he became leader in 1999.
It also said his close aides knew about his drink problem.
A party spokesman said the party had "quite properly" sought to protect Mr Kennedy's privacy.
Mr Kennedy resigned as Lib Dem leader in January this year after admitting his alcoholism for the first time.
The book, entitled Charles Kennedy: A Tragic Flaw, by the Times' political correspondent, Greg Hurst, says that when Mr Kennedy drank his hands would shake in the morning, he would perspire and exhibit flu-like symptoms.
"At its most acute, his drinking would leave him unfit to perform in public," the book said. Mr Kennedy would blame the smell on alcoholic mouthwash, it claimed.
Speaking for the first time about Mr Kennedy's illness, his secretary and closest aide for more than 20 years, Anna Werrin, says: "He drank in private, by and large, and drank more than he ought."
The book also alleges that the present Liberal Democrat leader, Sir Menzies Campbell, and other senior party figures agreed to keep quiet about Mr Kennedy's alcoholism after he came close to going public three years ago.
Fearful of possible newspaper revelations, Mr Kennedy made plans in July 2003 to reveal his alcoholism at a news conference with the aim of generating public sympathy, the book claims.
It says Sir Menzies was one of a handful of senior party figures informed about the planned announcement but, as he travelled from Edinburgh to London to attend the news conference, he was told in a telephone call that Mr Kennedy had changed his mind and that the public declaration was cancelled.
Sir Menzies and four Kennedy aides knew about the plan - Anna Werrin, Lord Razzall, Lord Newby and Jackie Rowley - and they all kept quiet about it, the book alleges.
It also claims that Lib Dem MP Matthew Taylor was part of a delegation who approached Mr Kennedy about his drink problem in 2004.
He reportedly told the former leader at the time: "You must never drink again. The next time you pick up a drink, you give up being leader."
Mr Taylor told BBC News 24 he and his colleagues had given the ultimatum "with a lot of heartache because he was not an unsuccessful leader" and had been "very popular with the public".
"We had a growing awareness of the problem. He had a growing problem and it takes a while - anybody who knows somebody who has had a problem with drink will know that," he said.
"There were occasions when he let himself down... We had to say to him, this cannot continue."
Commenting on his book, Mr Hurst said Liberal Democrats he had spoken to stressed Mr Kennedy was "a very private man, who wished to deal with this in private".
The former Lib Dem leader "was not incapacitated all the time" but "every now and then he would go on a spree of heavy drinking," Mr Hurst told BBC News 24.
Responding to the book, a Liberal Democrat spokesman said: "Senior Liberal Democrats quite properly and loyally sought to maintain Charles Kennedy's right to privacy and confidentiality while he was seeking to cope with his problem, for which he was receiving treatment.
"A point came early this year when a large number of Liberal Democrat MPs concluded that it was neither in Charles's nor the party's interest for him to continue as leader.
"The party is now united under Ming Campbell's leadership and is looking forward to building on its recent electoral successes."