A secret inquiry into bullying claims in the office of the Aged Care Minister Ken Wyatt has heard of staff being "scared" to work with an adviser who claimed to have a "special relationship" with the senior government frontbencher.

The minister has refused to release the findings of the inquiry - ordered by the then chief-of-staff to Malcolm Turnbull - prompting whistleblowers to reveal details of what they say was a toxic work culture "enabled" by Mr Wyatt.

Minister for Senior Australians and Aged Care and Minister for Indigenous Health Ken Wyatt and Prime Minister Scott Morrison. Credit:Alex Ellinghausen

The $37,000 investigation was conducted by a firm called CPM Reviews on behalf of the Department of Finance late last year and heard testimony from at least 10 staff members.

Transcripts of interviews with multiple former staffers obtained by The Sydney Morning Herald and The Age lay bare a culture of "intimidation" as a result of the "inappropriate influence" of senior adviser Paula Gelo over Mr Wyatt.