The BBC has confirmed Dr David Kelly was the source for the allegations that intelligence on Iraq was "sexed up".
It described him as "the principal source" for Andrew Gilligan's report and a second report for Newsnight
The corporation's director of news, Richard Sambrook, made the statement outside Television Centre.
Mr Sambrook said: "The BBC believes we accurately interpreted and reported the factual information obtained by us during interviews with Dr Kelly.
"Over the past few weeks we have been at pains to protect Dr Kelly being identified as the source of these reports. We clearly owed him a duty of confidentiality.
"Following his death, we now believe, in order to end the continuing speculation, it is important to release this information as swiftly as possible. We did not release it until this morning at the request of Dr Kelly's family."
He added: "We continue to believe we were right to place Dr Kelly's views in the public domain.
"However, the BBC is profoundly sorry that his involvement as our source has ended so tragically."
Prime Minister Tony Blair and his media chief Alastair Campbell faced calls to quit over his death.
But the BBC's admission lifts pressure on them and calls into question Mr Gilligan's report.
Dr Kelly told MPs he was not behind the key accusations it contained.
His close friend Tom Mangold has questioned whether he ever made the claims - and said even if he did they were not true.
The Corporation has been accused of increasing pressure on the weapons expert by refusing to say whether he was the source up until now.