Embattled employment minister Michaelia Cash has told senators she's too busy to face a third day of questions, after the Senate Employment Committee agreed to recall Senate Estimates on Friday.

The committee will sit in Parliament House from 9am to 4pm, to ask the Registered Organisations Commission (ROC) and the Australian Building and Construction Commission questions over the unravelling scandal.

Cash, however, told committee members she could not be in attendance because she had long-standing commitments in Perth. When asked if the minister could attend remotely, via phone or Skype, the committee was told she has commitments all day.

When BuzzFeed News called Cash's office, it could not confirm negotiations between Cash and the committee.

Cash has already faced two days of questions over BuzzFeed News' story that her office tipped-off media about the Australian Federal Police (AFP) police raids on Australian Workers Union (AWU) offices in Sydney and Melbourne.

Cash's senior media adviser David De Garis resigned from Cash's office on Wednesday night after the story was published, admitting to her that he was behind the leak.

Labor, the Greens and senator Derryn Hinch led the push for the committee to be recalled, as they believe Cash has failed to answer a number of questions about the leaks.

