Details of what was said on the eve of war have not been revealed
Releasing records of the cabinet's Iraq war meetings would do "serious harm" to war planning, says a government lawyer.
Cabinet Office counsel Jonathan Swift told a tribunal that minutes from March 2003 should be kept secret or ministers may become "more cautious" in cabinet.
But the Information Commissioner argued in favour of the minutes' release.
He said they were "highly material" to whether legal advice on the eve of war had been properly considered. A decision is expected in January.
Addressing the final day of a three-day Information Tribunal hearing in south London, the Cabinet Office's counsel Jonathan Swift appealed for minutes from cabinet meetings on 13 March and 17 March 2003 not to be disclosed to the public.
The two meetings were the only two full cabinet discussions on the then Attorney-General Lord Goldsmith's advice that it was legal to go to war in Iraq.
The cabinet took the decision to go to war at the 17 March meeting, a day before the parliamentary debate took place and three days before British troops were in action in Iraq.
Mr Swift told the hearing that the issue of disclosure was one of "substance" and referred to "knowledge of who said what and who said how much about what on what occasion".
He believed more than adequate public scrutiny had been afforded to the issue and outlined the damage he thought disclosure would bring.
Ministers are most unlikely to give in... They could use a special provision of the Freedom of Information Act to overrule the Tribunal for the first time
BBC's FOI specialist
He said "a general risk of disclosure would do serious harm" to the decision-making process.
He argued that if the minutes were published "cabinets are likely to be more cautious how they approach the matter in the cabinet setting" when it came to "war and peace decisions".
Information Commissioner Richard Thomas's counsel, Timothy Pitt-Payne, said the minutes were the "most important record" that existed "to understand the deliberative process" behind the discussion of Lord Goldsmith's legal advice.
He said the case for releasing the documents in the public interest was "a very strong one," as "cabinet needs to be willing to test and challenge robustly proposals put forward".
He suggested the minutes could help answer whether the cabinet challenged the legal papers from the Attorney-General and whether they asked to see a background briefing.
He said the question to ask was if there was "a serious failure of cabinet government".
Mr Pitt-Payne said the disclosure of the minutes would be "highly material" to helping answer those questions.
He outlined what he said were existing threats to free and frank cabinet discussions, such as secret press briefings from colleagues, leaks and memoirs.
He said the "curtain of secrecy is permeable" already and that an "objective and comprehensive record" was preferable to "partial and self-serving" accounts.
On Tuesday the Cabinet Secretary Sir Gus O'Donnell told the Information Tribunal deputy chair Chris Ryan that he thought the disclosure of the minutes could impede free and frank future discussions.
The Cabinet Secretary revealed he did not want Campbell's diaries published
He argued that it would be possible to infer which minister said what, even though no views expressed during discussions are attributed in the minutes, according to Times journalist Sam Coates who was at the hearing.
Accounts of the March meetings already exist in at least five memoirs that have been published, including Tony Blair's former communications director Alastair Campbell's account of his time in Downing Street, The Blair Years.
Sir Gus, who had the job of vetting Mr Campbell's book, said that he regretted it being published at all and that he had been against its release, especially as Mr Campbell had been a special adviser and not a minister.
But he argued rules to stop publication would be tricky to create as it would difficult to come-up with penalties for non-compliance.
He said, in the end, it was the author's responsibility.
A Tribunal Services spokesperson told the BBC: "We anticipate a decision in January."
If the Tribunal rejects the government's case, Ministers can appeal.
"Ministers are most unlikely to give in... They could either use a special provision of the Freedom of Information Act to overrule the Tribunal for the first time," according to BBC's Martin Rosenbaum "or they could appeal to the High Court".
Should the onward appeal to the High Court fail, the final route of appeal is the House of Lords.