How did this row start?

Amid the fevered speculation in the build-up to war in Iraq, the government last September produced its long-awaited dossier of evidence about Iraq's weapons of mass destruction.

Among its claims - as highlighted in Mr Blair's foreword - was that Saddam Hussein's "military planning allows for some of the WMD to be ready within 45 minutes of an order to use them".

Last week, a senior British intelligence official told BBC News that the dossier was rewritten at the behest of Downing Street to make it "sexier".

The source said the 45 minutes claim was a "classic example" of how uncorroborated evidence was given undue prominence - especially as it came from only one source.

He said: "That information wasn't in the original draft. It was included in the dossier against our wishes because it wasn't reliable."

BBC defence correspondent Andrew Gilligan says three other people "in or connected with the intelligence community" have voiced concern to him over the past six months about misuse of intelligence material by Downing Street.

What was the government's reaction to the story?

Number 10 itself said "not one word of the dossier was not entirely the work of the intelligence agencies".

Tony Blair said it was "absurd" to claim that Downing Street had pressured the security services to "invent" evidence.

Critics say the government is missing the point - that some evidence was hyped up or spotlighted more than it should have been.

What have the intelligence services had to say about the debacle?

John Scarlett, head of the Joint Intelligence Committee, which oversees security service reports for the government, has apparently let it be known he had no bust up with Downing Street over the dossier.

And what's this about the government talking about "rogue" elements in the intelligence services briefing against the government?

With the government looking rattled over the affair, cabinet minister John Reid accused "one or two unnamed, unappointed, anonymous people with uncorroborated evidence" of making "scurrilous attacks" and impeaching the integrity of both the prime minister and intelligence chiefs.

Dr Reid, whose remarks have Downing Street's backing, called on critics to "put up or shut up" and said there was already 15 years of evidence about Iraqi weapons.

His comments have been likened by Labour peer Bernard Donoughue to the "febrile and rather paranoid atmosphere" which existed in Downing Street when he was an adviser to Harold Wilson, who feared MI5 were plotting against him.

So where does the row go next?

The heat was on Tony Blair as stuck by the weapons evidence at prime minister's questions on Wednesday.

He is now facing more scrutiny from backbenchers as he makes a statement on the G8 summit in the Commons on Wednesday.

Two parliamentary select committees are launching inquiry into the weapons evidence.

MPs on the Commons foreign affairs select committee will conduct as much of their questioning as they can in public.

But the Intelligence and Security Committee, which is appointed by the prime minister and has wide-ranging access to top secret intelligence reports, meets behind closed doors. The government deletes "sensitive material" from the committee's reports before they go public.

Are those inquiries enough to satisfy critical MPs?

No. Many MPs want a full public, independent inquiry, something Number 10 is resisting.

The critics point to the precedent of the inquiry headed by Lord Franks in the wake of the Falklands War.

And others want public hearings in front of a judge, like the Scott inquiry into arms to Iraq, something Labour made great play of in opposition.