The potentially damaging information emerged in government documents released on Wednesday to an inquiry into the apparent suicide of weapons expert David Kelly.
The scientist was sucked into the heart of a furious row between Blair's government and the BBC over whether intelligence was "sexed up" for political ends.
Kelly was exposed as the source for a BBC journalist's report, which accused Blair's inner circle of hyping evidence about Iraq's weapons capability to win over a sceptical public.
An official note, written on July 14, the day before Kelly was due to testify to a parliamentary committee, made clear the expert would be told to keep his views to himself.
It said the respected scientist was due to be briefed later that day by the deputy chief of defence intelligence about his appearances in front of the foreign affairs committee and intelligence and security committee on July 15 and 16.
Separate documents revealed the top civil servant at Britain's Ministry of Defence had said at a meeting in Blair's office one week earlier that some of Kelly's views would be awkward for the government.
"If he was summoned to give evidence, some of it might be uncomfortable on specifics such as the likelihood of there being weapons systems ready for use within 45 minutes," the defence civil servant said at the meeting.
Dubious nuclear trigger
The inquiry heard how Blair's official spokesmen proposed ways to tighten the draft dossier's evidence on Saddam Hussein's intent to use banned weapons.
"The weakness obviously is our inability to say that he (Saddam) could pull the nuclear trigger any time soon," Tom Kelly said in one of many emails written by Downing Street
staff and shown to the inquiry which is expected to sit for the next few weeks.
Blair's claim that Iraq could deploy chemical or biological weapons at 45 minutes' notice was the most dramatic part of his September 2002 dossier aimed at winning support for a war most Britons opposed.
But the failure to discover such weapons - along with Kelly's suicide - has undermined trust in Blair's government and created the worst crisis of his six-year tenure.
An ICM poll for the Guardian newspaper on Tuesday showed 52% of the public trust neither the government nor the BBC to tell the truth and that only 6% trust Blair's administration more than the public broadcaster.