The firm of private investigators hired by Telegraph Media Group to discover the source of Vince Cable's leaked comments to the BBC have a "strong suspicion" that Will Lewis, a senior executive at Rupert Murdoch's News Corporation, was involved in orchestrating the disclosure, according to the Reuters news agency.

In an undercover audio recording leaked to the BBC, Cable told two Daily Telegraph reporters in December that he had "declared war" on Murdoch by referring his controversial BSkyB bid to the media regulator, Ofcom. The disclosure saw Cable immediately stripped of his ministerial responsibilities for the deal, which were handed to the culture secretary, Jeremy Hunt.

An investigation by Kroll, published in part by Reuters on Friday, concluded that there was a strong suspicion that Lewis and another former Telegraph colleague – who also joined News Corp's UK publisher subsidiary News International last year – were "involved in orchestrating the leak of information" in order to damage their former employer.

TMG, the publisher of the Telegraph, and News International declined to comment. Kroll had not responded to a request for comment at the time of publication.

News Corp's management and standards committee – where Lewis currently works – said it had "no comment to make" on the Kroll report while friends of Lewis dismissed the Kroll document as "totally bizarre".

Lewis has relinquished his responsibilities as News International general manager and been seconded to News Corp's MSC, which is investigating alleged phone hacking and payments to police officers by the now-defunct News of the World.

Kroll's report, which the Guardian believes to be genuine, concludes: "Given their employment with News International, their antipathy toward the Telegraph, and their knowledge of the story, we have a strong suspicion that [the other former Telegraph employee] and Lewis were involved in orchestrating the leak of the information."

The Daily Telegraph published a story based on extracts of the undercover recording of Cable on 20 December, but omitted the minister's comments about Murdoch. Cable's remarks were first revealed by the BBC's business editor, Robert Peston, online and on the BBC News channel. The BBC also ran an audio recording of his comments to the Telegraph reporters.

Kroll's investigators apparently said the leak was likely the result of "unauthorised access" to TMG's IT systems. It said: "The copying of the audio file by either of these methods constitutes theft."

The report continues: "We have established that on 9 December, the circle of knowledge of an impending 'big story' by the same Telegraph team who broke [a major political story about British parliamentary expenses] extended to ... a former Telegraph employee now employed by News International ... [who] works closely at News International with the former Telegraph editor Will Lewis, both of whom have strong motivations to damage the Telegraph.

"In the period between 9 and 21 December there was extensive telephone, text and social contact between [the former Telegraph employee], Lewis, and individuals within the authorised circle of knowledge ... [we] believe it is more than likely that their knowledge of the big story grew. News International was the only media organisation we identified as having extensive contacts with the authorised circle of knowledge during this period."

According to Reuters, Kroll found that whoever leaked the recording "had to have the help of someone who could access the audio file".

However, Kroll investigators warned TMG that pinpointing the exact source of the leak would be difficult because too many people had access to the IT system.

Kroll apparently advised TMG executives to halt the investigation after it discovered that 15 of the paper's employees and up to 50 BT staff could in theory have access to the system because of outsourcing.

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