Turnbull backs Cash over rumour threats

Malcolm Turnbull says Michaelia Cash was being "bullied" when she threatened to expose rumours about Bill Shorten's female staff.

The prime minister backed Senator Cash after Labor demanded she apologise and resign over the comments she made in a Senate hearing on Wednesday.

"Senator Cash was being bullied and provoked by Senator (Doug) Cameron, who was making insinuations about staff. She made a response which she has unreservedly withdrawn," Mr Turnbull told parliament on Thursday.

In a Senate estimates hearing, running parallel to question time, Labor senator Jenny McAllister sought to ask Senator Cash about Mr Turnbull's comment.

However, the committee hearing was adjourned to hold a private meeting to discuss whether the line of questioning could go ahead.

Earlier, when Senator Cash entered the committee room for the hearing, a whiteboard was put across the corridor to bar television cameras from filming her entry.