No vacancy for Costello as chairman: Cormann

Finance Minister Mathias Cormann has attempted to hose down suggestions former treasurer Peter Costello is being lined up as the next chairman of the Future Fund, declaring there is "no vacancy" for the $92 billion investment fund.

But in a fiery Senate estimates committee meeting, Senator Cormann declined to clearly answer whether he had spoken with Mr Costello regarding the role, describing the question as "hypothetical'.

The job is held by David Gonski, who was initially tasked to find a replacement for founding chairman David Murray. Mr Costello established the Future Fund in 2006 and serves on its board.

Questioned by Labor Senator Penny Wong whether he had spoken with Mr Costello about chairing the fund, Senator Cormann said Mr Costello was among the people he met regularly.

"But as I've pointed out before, there is no vacancy," he said.

"This is completely a hypothetical question and you know it."

The fund was established with $60.5 billion in government contributions to help pay for the unfunded superannuation liabilities of public servants. It has a mandate to return inflation plus 4.5 to 5.5 per cent a year over 10 years.

The hearing was told the government had not injected money into the fund since 2007, and the gap between its liabilities and assets would continue to grow.

Outgoing managing director Mark Burgess told senators there was no date for his departure yet as a replacement had not been found. Chief investment officer David Neal confirmed the fund had sold all of its tobacco investments.

The Melbourne-based fund recently announced it had returned 8.2 per cent a year over five years and 9.7 per cent a year over the past three years.

Over the year to September, the fund lowered its investments in cash, alternative assets and debt securities and boosted its exposure to domestic and overseas shares, private equity and infrastructure and timberland.