Derek Draper, the former aide at the centre of the attack blog scandal, was cut adrift by Labour yesterday as ministers were braced for the publication of further damaging e-mails.

Plans to smear David Cameron and other leading Tories that were disclosed in an electronic exchange between Mr Draper, who runs a pro-Labour website, and Damian McBride, the former Downing Street aide, have already seriously embarrassed Gordon Brown.

Ray Collins, Labour’s general secretary, came close to acknowledging in a letter to members of the National Executive Committee that further slurs against senior Conservatives had been mooted. Mr Draper’s advice will not be sought in the future, he said, adding that he did not take advice advocating smears or personal attacks. Senior party sources fear that publication of further e-mails from Mr Draper could gravely embarrass ministers and undermine attempts to portray Mr McBride as a lone rogue.

Conservatives accused Downing Street of a whitewash after Sir Gus O’Donnell, the Cabinet Secretary, rejected a request for an official inquiry in the affair.

In his reply to Francis Maude, who shadows the Cabinet Office, Sir Gus, the head of the Civil Service, repeated that Mr Brown had been “assured that no minister or political adviser other than Damian McBride had any involvement in the e-mails which were covered in the weekend’s newspapers”.

The Tories had called for an investigation into whether Tom Watson, the Cabinet Office Minister, had known of the planned Red Rag website, where the slurs were to have been published. Mr Watson has issued a denial of any knowledge of the site through lawyers. “Tom Watson has made his own position clear,” Sir Gus wrote.

Mr Maude is understood to have written back to the Cabinet Secretary asking whether he had been able to access the No 10 e-mail accounts to check the claim that no one else had known about plans to smear Tories. “He says that there have been assurances but from whom and on what basis?” one senior source asked. “The impression Downing Street is giving is that this was a rogue initiative. We are not convinced of that fact.” The Tories will pursue their own investigation through freedom of information requests and parliamentary questions.

In an interview yesterday Mr Draper, a former aide to Lord Mandelson, appeared to acknowledge that he had helped to set up the Red Rag website, which was registered to an address in the House of Commons. It is not clear, however, who else was involved or knew of its existence.

Mr Collins, in his letter to senior Labour figures, admitted that Mr Draper acted as an official adviser until recently. “He subsequently left Victoria Street to set up the Labourlist blog,” Mr Collins wrote. “Since then he has offered advice and opinion on an ad hoc basis which ended in March and will not be sought in the future.”

Mr Collins came close to acknowledging further slurs had been made, saying in his letter to the NEC: “I receive advice and opinion from many Labour Party supporters in my work as general secretary but I decide what advice I take or seek and act in a manner appropriate with my values and those of the party, which certainly does not include smears or personal attacks. I want to reiterate that Derek Draper does not hold a position or role with the Labour Party and this will remain the case.”

Mr Brown will make his first public appearance today since the scandal broke, in Glasgow. He is bound to face renewed calls to issue a personal apology for the actions of his disgraced spin doctor. The Prime Minister has so far refused to go beyond expressing regret over the affair. One senior colleague suggested yesterday that Mr Brown should go further, however, saying: “There’s a collective responsibility here.”

Ed Balls, the Schools Secretary, said he thought the e-mails were vile, despicable and horrible but all parties needed to raise standards. “I think all of us in politics, in the Labour Party and all political parties, need to look in ourselves . . . and the people we employ, the activities they’re undertaking, the things they are doing.”

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