Justice secretary Jack Straw has refused to release the minutes from a cabinet meeting which discussed the invasion of Iraq in 2003.
Straw caused anger in the Commons by stating that he would use a ministerial veto to stop the minutes from being published.
The justice secretary was met with shouts of "shame" and "disgraceful" from opposition benches as MPs heard the news.
But he stated that allowing information on the Iraqi invasion into the public domain "risked serious damage to cabinet government".
He added that the potential harm "far outweighed" any benefit to the public.
In his Commons statement, Straw said: "Cabinet is the pinnacle of the decision-making machinery of government.
"It's the forum in which debates on the issues of greatest significance and complexity are debated.
"Whether the nation was to take military action was indisputably of the utmost seriousness.
"However, I disagree with the reasoning of the majority of the tribunal.
"In their decision they refer to the momentous nature of the decision taken, the public interest in understanding the approach to that decision and in the accountability of those who took the decision."
Last month, the Information Tribunal recommended that details of the discussions in 2003 between ministers should be made public.
But Straw stated: "In my judgment that analysis is not correct. The convention of Cabinet confidentiality and the public interest in its maintenance are especially crucial when the issues at hand are of the greatest importance and sensitivity."
25 February 2009