Gordon Brown was "furious" when he found out about the smear emails written by a key aide about top Tories, his spokesman has said, amid renewed Tory pressure for an inquiry into the scandal.
And he said there was now a "huge amount of frustration" in Downing Street that the controversy was diverting attention from efforts to deal with the country's problems such as the recession.
The author of the emails, special adviser Damian McBride, quit on Saturday when the story emerged and will not receive any severance pay, the Prime Minister's spokesman confirmed.
Mr Brown, who accepts that none of the allegations made about Conservatives including David Cameron were true, has written to the subjects of the emails expressing "regret" but not offering any personal apology.
Cabinet colleagues insisted he had done everything he needs to do and cannot be held responsible for the actions of Mr McBride, one of his closest advisers for almost a decade.
The PM's spokesman repeatedly batted away questions about whether Cabinet Office Minister Tom Watson was aware of plans to set up a left-leaning gossip website to be called Red Rag - where the mooted slurs against Tories were designed to be published.
The PM said he had full confidence in Mr Watson but when asked whether the minister had been aware of the plan, he said simply that there was "nothing to add" to the statement made over the weekend by Mr Watson. In that, he said he had not been aware of the offending emails and had no involvement in "discussions to create the Red Rag website. I had no such involvement".
Shadow cabinet minister Francis Maude has written to Cabinet Secretary Sir Gus O'Donnell seeking answers to what the Opposition say are a number of unanswered questions surrounding the affair, including any possible role played by Mr Watson.
David Cameron later said Mr Brown bears personal responsibility for creating the sort of culture that allowed a senior Downing Street aide to consider smearing senior Tories.
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The Conservative leader said only a change of Government would bring an end to such "nonsense". "What this whole episode demonstrates is the need for change. Not change in the special advisers code but change in the culture at Number 10 Downing Street," he said
