The department of communications on Monday went on the offensive against the Sunday Times, accusing the newspaper of “peddling slander and salacious rumours” in a “desperate attempt to convict” the minister “in the court of public opinion”.

The department’s newly appointed spin doctor, Wisani Ngobeni, made the comments at a press conference in Pretoria, a day before communications minister Dina Pule is scheduled to appear before parliament’s ethics committee for the second time. The committee is investigating allegations that the minister’s alleged romantic partner, Phosane Mngqibisa, benefited to the tune of R6m from the ICT Indaba organised by the department last year.

“We wish to state categorically that we do not have the documents that the Sunday Times relied upon for their story,” Ngobeni told the press conference, reading from a prepared statement. “We do not know the source of these documents and we do not have these documents on our records. We are unable to express a view on documents which we do not have knowledge of.”

Pule is the subject of investigations by both the ethics committee and the public protector. The latter is expected to present the findings of its investigations by the end of this month.

Ngobeni said on Monday: “For the record, the department wishes to reiterate that none of the allegations levelled against minister Pule and the department by the Sunday Times will stick. In the 10-month campaign against minister Pule and the department, the Sunday Times has failed to link minister Pule and the department to any wrongdoing because none exists.”

The newspaper at the weekend published a story that it said showed that Pule was romantically linked to Mngqibisa and that the two were more than simply “comrades” as they had claimed.

Two weeks ago, Pule called a press conference at which she attacked the Sunday Times, levelling sensational allegations against three of South Africa’s top investigative journalists, Mzilikazi wa Afrika, Rob Rose and Stephan Hofstatter, and suggesting Wa Afrika had attempted to blackmail her.

She said the journalists had engaged in a smear campaign against her in an effort to ensure their own business and political connections benefited from the awarding of a lucrative tender for the manufacture of government-subsidised set-top boxes for digital terrestrial television.

On Monday, Ngobeni said that the Sunday Times appeared to be “determined to exploit the principled position of the department and minister Pule by continuing to wilfully mislead, manipulate facts and distort information in their passionate public crusade against [the] minister and the department. The department will not respond to these issues through the media but through legitimate processes in parliament and the public protector.”