Labour threatened Clare Short with the sack by barring her from standing in her Ladywood constituency, the rebel MP has revealed.
Party enforcers tried to "muzzle" her by threatening to stop her standing in last year's General Election, she said.
And she revealed how she kept a secret diary in the run-up to the Iraq war, when she was quizzed by a Commons committee yesterday.
The Labour MP for Ladywood was International Development Secretary in Tony Blair's Cabinet but resigned in May 2003, shortly after the conflict ended.
She became an outspoken critic of the war and of Mr Blair, claiming he was "obsessed with his place in history".
She published a book detailing her time in the Cabinet, An Honourable Deception, in October 2004, in the run-up to the General Election in May 2005.
But she revealed yesterday that she released the memoirs in response to a "pretty crude" attempt to stop her talking.
She said: "I didn't intend to write a book so quickly. But there was a very sharp attempt to muzzle me."
Hilary Armstrong, the Labour Chief Whip, threatened to remove the party whip, which meant she would be barred from standing for re-election as a Labour candidate.
"The Chief Whip threatened me with withdrawal of the whip, which meant I couldn't stand as a Labour candidate."
She was also sent a letter warning her comments could be in breach of the Official Secrets Act, she said.
"It was a very harsh and deliberate attempt to silence me.
"The Chief Whip tried to get me to agree to say nothing that was in any way critical of the Prime Minister."
As a result, she wrote the book in four months, to ensure the story of the Iraq war was told.
"There was deceit, and Parliament absolutely failed to deal with the deceit.
"It was very important for those truths to come out," she said.
It was based partly on a diary she started to keep while she was in the Cabinet, unknown to her colleagues.
However, she had not originally intended to publish the diary, she said.
"I had no intention of doing a book. It was just I was living through enormous turbulence, historical events."
Ms Short said that despite her disagreements with the Labour leadership, she had dedicated most of her life to the Labour Party and took the possibility of having the whip withdrawn very seriously.
Ms Short was giving evidence to the Public Administration Committee, chaired by Cannock Chase MP Tony Wright (Lab).
It is conducting an inquiry into the rules regarding what politicians and civil servants can reveal in their memoirs.
Also giving evidence were former Chancellor Lord Lawson, former Foreign Secretary Lord Owen and Sir Jeremy Greenstock, Britain's former ambassador to the United Nations.
Sir Jeremy, who was also Britain's special representative in Iraq for six months after the war, wrote a book about his experiences with the Foreign Office but it has never been published because of objections from Jack Straw, the Foreign Secretary. ..SUPL: