The High Court challenge to the postal vote on same sex marriage could be heard as early as today.

The Prime Minister Malcolm Turnbull is selling the vote as a chance for "all Australians to have their say" on the issue.

But many are questioning whether the Australian Bureau of Statistics (ABS) is the right body to oversee the process.

The ABS itself is still deferring questions on the vote to the acting Special Minister of State, Mathias Cormann.

But some have suggested that the task may be beyond the capacity and the authority of the Bureau — among them is Bill McLennan, a former Chief Statistician for the ABS.