Almost 85 per cent of LGBTIQ Australians remain opposed to a plebiscite on same-sex marriage, with a majority against a nationwide vote even if it means no change to the law under the Coalition government.

A survey of 5500 LGBTIQ people in late July, considered the largest of its kind, found opposition to a plebiscite among men and women, all age groups and in every state and territory.

When asked whether they supported or opposed a plebiscite on marriage equality, 84.7 per cent of participants said they were opposed, with 71.5 per cent strongly opposed.

Just 9.9 per cent supported a plebiscite, including 6.5 per cent who strongly supported it, while 5.4 per cent were undecided.