One of Britain's most senior spies has defended the inclusion of the controversial 45-minute claim in the government's dossier on Iraqi weapons of mass destruction.

Giving evidence to the Hutton inquiry, Sir Richard Dearlove said the intelligence had come from an "established and reliable source".

And he said he had been "shocked" to hear that Dr David Kelly conducted unauthorised discussions on intelligence matters with journalists.

The head of MI6 also revealed that he had insisted on having the final say on any of his department's intelligence that was included in the September dossier last year.

Sir Richard described the suggestion that Iraq could launch weapons of mass destruction within 45 minutes as "a piece of well-sourced intelligence".

And he said the information had come from an "established and reliable source" who was quoting a senior Iraqi military officer who was in a position to know this information.

On September 4, as the dossier was being prepared, Sir Richard said he had discussed the matter with the prime minister's foreign affairs adviser, Sir David Manning.

"I discussed with Mr Manning to what extent it would be possible to put intelligence from my service into the public domain and I said that I thought it would be possible to put some of this into the public domain but I would insist, on grounds of source protection, in having the last word in withholding material from publication if necessary," said the spy chief.

"On September 4 it was clear that there was a certain amount of new material produced by my service which had not arrived in time to be included in the original draft that was put together.

"As far as I recall, I recommended that the draft be reworked to take account of this new material.

"A new draft, I think, was then put together and circulated to JIC [joint intelligence committee] members because there was quite a few changes. The resulting assessment was issued on September 9."

As the drafts of the dossier were circulated for comment, Sir Richard said he was not aware of any unhappiness with the wording.

"When we circulate a report, there is a procedure by which any reader can comment on the report or question its contents, and that is a mechanism that is frequently used," he said.

"The circulation of the report that included the piece about 45 minutes did not evoke any comment from customers at all."

Turning to Dr Kelly's tape-recorded conversations with BBC journalist Susan Watts, Sir Richard pulled no punches in saying they should not have taken place.

"Can I also say in respect of this recorded conversation, as chief of the service I am shocked to see someone discussing one of the CX [MI6 intelligence] reports - which is what he was discussing with a journalist - without authorisation."

He added: "It is a serious breach of discipline."