Australian Conservatives leader Cory Bernardi will unleash a million robocalls advocating a "no" vote, in what he describes as a survey of his constituents on same-sex marriage.

The calls will go out to home landlines in Senator Bernardi's home state of South Australia and neighbouring Victoria, where his party has an upper house MP.

Following the senator's spiel, respondents are asked to indicate how they are voting, which expert researchers have described as an example of push-polling.

"Hello, it's Senator Cory Bernardi calling from the Australian Conservatives, and I'd like to ask you something very important – so please, stay on the line for just a moment," the recording begins, in audio first published by Channel Nine.