Lord Brian Hutton's inquiry, which will likely last months, has emerged as a test not only of Britain’s reasons for going to war in Iraq, but also of Blair's leadership.
"You could say (Hutton) holds the fate of the government in his hands," Vernon Bogdanor, professor of government at Oxford University, told Reuters news agency.
Kelly, an expert on chemical and biological warfare and a former UN arms inspector in Iraq, was found dead on 18 July in woods near his home, west of London. One of his wrists was slit.
Sexed up dossier
He found himself at the centre of a political storm after being identified as the source of a BBC report that Blair's government "sexed up" an intelligence dossier about the threat of Saddam's weapons of mass destruction.
The failure to find any such weapons in the war-ravaged country some four months after Saddam's defeat is denting Blair’s popularity. The once-socialist prime minister was in 1999 Britain’s most popular premier since Sir Winston Churchill.
To compound Blair’s woes, Lord Brian Hutton said earlier this month that he proposed "at some stage" to summon Blair to his court.
Defence Secretary Geoff Hoon, Blair's close aide, Downing Street media strategist Alastair Campbell, and BBC board of governors chairman Gavyn Davies will also be asked to appear before the inquiry, Hutton said.
In a further twist, Blair’s official spokesman Tom Kelly last week suggested the dead weapons expert was a "Walter Mitty" fantasist. Kelly later apologized for his remarks.
Hutton has also said he wants to find out how Kelly was identified as the BBC’s anonymous source.
Claire Short, a former staunch Blairite and international development secretary, last month said the government was partially to blame for his death.
Blair strongly denied that he authorized the leaking of the scientists' name as the source of the BBC report.