Conservatives demanded an apology from British prime minister Gordon Brown after the resignation of a top adviser said to have sent emails suggesting a gossip campaign.
Damian McBride, who was head of strategy and planning in Mr Brown's Downing Street office, proposed in one email a "campaign of unfounded personal slurs" against senior Conservatives and their wives in an attempt to embarrass the opposition as an election approaches, the Sunday Timesnewspaper said.
Senior Conservative MP William Hague told Sky News: "We do want a clear apology from the prime minister himself."
"It's very important that he shows personally that he takes this very seriously and gives his assurance that this sort of thing is not going to happen again," he added.
"If that is not an orchestrated dirty tricks campaign, I don't know what is," added Conservative MP Chris Grayling, speaking to the BBC.
Conservative MP Nadine Dorries, who was mentioned in emails she described as false and libellous, said she was seeking legal advice.
The Conservatives, keen to play up the impression of a government in disarray as a general election looms within the next 14 months, have stepped up their attacks on Mr Brown.
Opinion polls show the Conservatives leading Labour by at least seven points as Mr Brown grapples with the financial crisis, a severe recession and rising unemployment.
Mr Brown's office has said the prime minister knew nothing about the emails, sent by McBride from a Downing Street account.
"It is the prime minister's view that there is no place in politics for the dissemination or publication of material of this kind," a statement from his office said.
The revelation is embarrassing to Mr Brown, after a scandal over interior minister Jacqui Smith, who said she mistakenly submitted an expense claim for pornographic films viewed by her husband.
The controversy detracts from the image Brown seeks to present of a statesmen leading the response to the global financial crisis.
The existence of the emails was initially disclosed by a political blogger, who did not reveal how he obtained them.
The recipient of the emails, Derek Draper, has said McBride sent them after Mr Draper asked friends if they knew of any "good gossip" about Labour's opponents for a blog he was considering launching. The blog never got off the ground.
Mr Draper apologised on Sunday to people mentioned in the "juvenile emails."They said the episode showed Brown's government had broken its promise to end the culture of news management or "spin" for which his predecessor, Tony Blair, was heavily criticised.
Reuters