A senior figure in business innovation has dismissed reports that he is to become Foreign Secretary David Miliband's chief of staff in a future leadership challenge.

Jonathan Kestenbaum, chief executive of the National Endowment for Science, Technology and the Arts, said the story in PR Week was "complete fabrication".

The magazine reported that Mr Miliband would find a place "for Jonathan Kestenbaum, the well-connected chief executive of Nesta. Kestenbaum is said to have told friends he would take [the job of] chief of staff."

But this week Mr Kestenbaum, a former chief executive of UJIA, ex-director of the Chief Rabbi's Office, and one-time chief of staff for Sir Ronald Cohen, said: "I have known David Miliband for years. He is an old family friend. But this story is absolutely unsourced and is a fabrication of a fabrication."

He acknowledged, however, that he had not contacted the magazine to deny the report on the record.