London ? Prime Minister Tony Blair, facing the biggest crisis of his six years in office, denied Thursday that the government “sexed up” a dossier on Iraq’s weapons threat, and said he would have resigned if it had been true.

Blair was testifying at a judicial inquiry into the apparent suicide of David Kelly, a weapons expert named as the source of a BBC story that said the government knowingly exaggerated the Iraqi threat in the September dossier.

“This was an attack that went not just to the heart of the office of the prime minister but also the way our intelligence services operated,” Blair said. “It went, in a sense, to the credibility, I felt, of the country.”

Blair said the British Broadcasting Corp. story attacked his integrity and led Britons to believe that his government duped them about the threat of Iraq’s weapons of mass destruction as the U.S.-led coalition built its case to invade Iraq.

Among other charges, the May 29 BBC report said Blair’s aides had inserted a claim into the dossier on Iraq’s biological and chemical weapons saying they could be deployed in 45 minutes. The BBC report, citing an unidentified source later revealed to be Kelly, said the government knew the claim was false and some intelligence agents had disputed it.

“This was an absolutely fundamental charge,” Blair said. “This was an allegation, were it true, that would have merited my resignation.”

Blair became only the second prime minister to ever testify at such a hearing. The first was his immediate predecessor, Prime Minister John Major, who appeared at a 1994 inquiry studying whether the government violated its own policy on weapons sales to Iraq under Margaret Thatcher.

The public spat between the government and the BBC has focused the nation on a debate about the failure to find any weapons of mass destruction since Saddam Hussein was ousted.

The dispute about the report and the inquiry have knocked Blair’s popularity to its lowest levels in his six years in office and left many Britons questioning his reliability, according to recent polls.

The dispute produced front-page headlines last month when Kelly, 59, a former U.N. weapons inspector in Iraq and a government adviser, was identified as the possible source of the BBC report. Three days after he testified before a parliamentary committee, Kelly was found dead near his home, his wrist slashed.

The inquiry is trying to determine how the government came to expose Kelly — a move that placed him under intense media pressure and led him to testify before the committees. Whatever the finding, few believe that Blair is likely to step down, even if his government is criticized for the way it treated Kelly.

A member of the Stop The War Coalition holding a giant playing card like those used by the U.S. forces to depict members of Saddam's regime protests outside the Royal Courts of Justice in London. British Prime Minister Tony Blair, pictured on the card, testified Thursday as part of a hearing on the death of British weapons expert David Kelly.