Mr Collins denied any knowledge of the e-mail campaign
The Labour Party's general secretary attended a meeting on online strategy with the men caught up in the e-mail smear campaign row, it has emerged.
Ray Collins met Gordon Brown's aide Damian McBride and ex-spin doctor Derek Draper a month before the e-mails were sent, the News of the World reported.
Mr Collins admitted being at the meeting but said he had "no knowledge whatsoever of any smears".
The Tories said the whole "culture" within No 10 must be changed.
Shadow chancellor George Osborne, one of the victims of the smears, told the BBC's Andrew Marr show that Gordon Brown must be "held to account" for how people around him behaved.
George Osborne on personal smears against political opponents
Mr McBride, a close aide of Mr Brown's resigned over his suggestion that senior Tories could be smeared, leading the prime minister to personally apologise for his behaviour.
Mr Brown has stressed that neither he nor any other minister knew of what Mr McBride was doing.
Asked about Mr McBride's e-mails, Mr Collins said he "found the stories and reports of the last week absolutely disgusting."
Mr Collins said his meeting with Mr McBride and Mr Draper took place at the premises of the union Unite in December, after the Red Rag website at the centre of the scandal was set up.
Mr Collins said it was to "discuss online digital campaigning and how we could support and encourage left-of-centre websites and bloggers".
Gordon Brown has to live with the regime he runs out of Downing Street
He added: "This meeting was not about scurrilous rumour, personal attacks or smears as I would have been furious that such things could be seen as legitimate tools of political debate. As the PM has made clear, there is no place in politics for this kind of activity."
The newspaper also claimed former Labour spin doctor Charlie Whelan, union official Andrew Dodgson and journalist Kevin Maguire were at the meeting.
Mr Maguire, associate editor of the Daily Mirror, told the BBC he was at the meeting - but backed Mr Collins' position.
He said: "I went to two meetings, discussions about Labour internet campaigning and so on. And I was at this one with Ray Collins.
"And I can say categorically that smears were not discussed."
But the Conservatives said the meeting "suggested" that knowledge of a potential smear campaign against them extended beyond Mr McBride.
"Gordon Brown has to live with the regime he runs out of Downing Street," Mr Osborne said, describing the attacks on him and his family as "very unpleasant and particularly personal".
Kevin Maguire: 'I can say categorically that smears were not discussed'
"Gordon Brown is responsible for the culture he created in Downing Street. That culture has to end."
Former Labour leader Lord Kinnock said he believed Mr Collins was "entirely innocent" of any involvement with the smear campaign and was being "sucked into the maelstrom" surrounding the affair.
He told the BBC that Labour had been damaged by the activities of a small number of what he described as "repulsive people" who "lived by the sword and died by the sword".
"The awful thing is the damage inflicted on the government of this country," he said.
However, he said "no judgement" should be made on Gordon Brown and his values as a result of the affair.
Olympics minister Tessa Jowell said the latest allegations regarding the smear campaign were "lurid and terrible".
But she told Sky News that they did not reflect the values or the work of the majority of people within the Labour party.
But the BBC's political correspondent Vicki Young said the affair was threatening to spiral out of control and deflect attention from Labour's efforts to fight the recession.
Meanwhile three separate polls have suggested Labour's support was being affected by the smears row.
A survey conducted by Marketing Sciences Ltd for the Sunday Telegraph showed Labour on 26%, down five points from three weeks ago. The Conservative rating of 43% would give leader David Cameron a 120 seat majority at a general election.
A poll in The Mail on Sunday also put Labour on 26%. A third of those questioned in the survey, carried out by BPIX, thought Gordon Brown's government was sleazier than the last Conservative administration - compared to 23% who said it was less sleazy.
Some 54% of people questioned in an Ipsos Mori survey for the News of the World said that the smear campaign row would affect the way they vote, compared to 42% who said it would not.
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