Downing Street communications chief Alastair Campbell acknowledged yesterday that he had seen Dr David Kelly as the key to resolving the Government's bitter battle with the BBC over the Iraq weapons dossier.

Mr Campbell told the inquiry into the scientist's death that he had believed Dr Kelly could prove that a BBC report claiming the Government "sexed up" the dossier was false.

However, he strongly denied that he had been responsible for leaking his name to the Press.

The inquiry, headed by Lord Hutton, was set up to investigate how weapons expert Dr Kelly apparently came to take his own life after being identified as the source of the report by BBC journalist Andrew Gilligan on May 29.

In his keenly awaited appearance before the inquiry, Mr Campbell denied he had been responsible for inserting into the dossier a controversial claim that some Iraqi weapons could be deployed within 45 minutes.

He insisted that the dossier had been the work of John Scarlett, chairman of the Joint Intelligence Committee, although he admitted that he had advised on "presentational" issues.

However, much of the questioning by counsel to the inquiry James Dingemans QC focused on how Dr Kelly was handled by ministers and senior officials after he admitted having had an unauthorised meeting with Mr Gilligan.

Mr Campbell repeatedly spoke of his anger and frustration at the continuing refusal of the BBC to accept that its story was wrong.

He said that when Defence Secretary Geoff Hoon told him on July 4 that Dr Kelly had come forward, he immediately thought that the scientist could enable them finally to prove the story was untrue.

"I felt that if this person was the source, then it probably was the only way in which we were going to be able to establish the truth," he said.

Mr Campbell denied a suggestion that Dr Kelly had been caught in the middle of a "game of chicken" by the Government and the BBC. No one had ever thought that it would end with Dr Kelly's death.

"The impression I got was of a very strong, resolute character, clearly of deep conviction, who had been in among difficult, stressful circumstances before, and I don't think it crossed anybody's mind it could take the turn it did," he said.

Initially he had not known Dr Kelly's identity, although he was aware that he was not a member of the intelligence agencies as some BBC reports had appeared to suggest.