Former High Court judge Michael Kirby says a postal plebiscite on same-sex marriage makes him feel like a second-class citizen.
Mr Kirby labelled as unacceptable the Turnbull government's decision to ask the Australian Bureau of Statistics to run a non-binding, voluntary ballot in the coming months.
"It really is a shocking thing to me we're thinking of putting this into our law-making process in Australia," he told ABC radio on Thursday.
"I feel as a citizen I'm being treated in a second-class way."
Mr Kirby, who is happy to wait to wed his partner of 50 years instead of having the public postal vote, wants the plan to be abandoned.