An influential group of MPs is set to scrutinise the government's decision to go to war with Iraq.
Blair returns from G8 conference
In particular it will focus on the way intelligence information over Iraq's weapons of mass destruction (WMD) was presented by Tony Blair's administration.
The announcement by the Foreign Affairs Select committee will add to the pressure on Number 10 which is facing questions as to why coalition forces have failed to find WMD in Iraq.
The prime minister is also expected to announce on Wednesday that Parliament's Intelligence and Security Committee will investigate the issue of Iraq's WMD.
The Foreign Affairs committee - chaired by Labour's Donald Anderson - will consider whether the government presented "accurate and complete information to Parliament" in the period leading up to military action in Iraq.
Mr Anderson said the inquiry had been called out in the public gaze and would want to meet "all relevant" witnesses - that could include Mr Blair's director of communications Alastair Campbell.
Referring to the proximity of the intelligence committee to Mr Blair, he said: "There would be a credibility problem with them which there would not be with our inquiry."
Intelligence and security committee is appointed by and reports to the prime minister, although it prides itself on its independence. It meets behind closed doors.
Foreign affairs committee is a cross-party select committee and meets in public.
The Foreign Office has already said it will co-operate with the inquiry.
Downing Street has rejected growing calls for a full public inquiry into its pre-war claims about Saddam Hussein's weapons capability.
Mr Blair also rejected a demand from Tory leader Iain Duncan Smith to deliver a statement to MPs on Tuesday evening saying he would answer any questions when he appeared before the Commons on Wednesday.
The prime minister is to make a Commons statement about the weekend's G8 summit in Evian, which was dominated by the issue of WMD.
Mr Blair has denied accusations that this contained intelligence information which had been doctored, insisting he stands "100%" by the evidence shown to the public about Iraq's alleged weapons programmes.
That was not enough to stop Lib Dem leader Charles Kennedy and Dame Pauline Neville-Jones, the former head of the Joint Intelligence Committee, joining the expanding list of those demanding an independent inquiry.
Calls for a probe have grown since ex-cabinet minister Clare Short said the prime minister had "duped" the country into going to war.
Former Labour chancellor Lord Healey said he believed the US and UK governments had "twisted" evidence put forward by intelligence services.
I suspect that in presentational terms, Number 10 has gone for the greatest, most arresting presentation of the facts
More than 70 Labour MPs have signed a Commons motion calling for the publication of the full government evidence on Iraqi weapons.
Shadow foreign secretary Michael Ancram, who made the request, said the allegations about WMD "strike at the heart of the integrity of both the government and our intelligence services".
It has also emerged that Mr Straw was flying back early from a meeting of Nato foreign ministers in Madrid after the Liberal Democrats announced they would be using their opposition day debate in the Commons on Wednesday to discuss Iraq.
Further pressure came as the US Congress ordered an investigation into possible abuse of intelligence information about alleged WMD in Iraq.
Labour MP Brian White admitted he was swayed to abstain rather than vote against the government over Iraq, because of the arguments over WMD.
Earlier, in Evian, Mr Blair said: "Frankly, the idea that we doctored intelligence reports in order to invent some notion about a 45-minute capability for delivering weapons of mass destruction is completely and totally false."
He appealed for people to have a "little patience" as an international survey group was this week starting to interview Iraqi scientists and investigate potential arms sites.
UK experts believed two mobile biological weapons facilities had been found, and were part of a whole series of similar units, he added.