The New South Wales state government is planning to introduce a bill to lower the gay age of consent to 16 - bringing the state into line with jurisdictions in Australia and overseas, said Attorney-General Bob Debus announcing a conscience vote on the issue for Labor MPs.

Opposition leader John Brogden has previously supported changing the laws and will also allow Liberal MPs a conscience vote.

According to The Sydney Morning Herald, the amended bill will however include safeguards, including the toughening of penalties for offences on children under 16, and the removal of the defence of not knowing a child was underage.

"There is no discernible benefit in maintaining an unequal age of consent, there is however a substantial cost in allowing that inequity to be perpetuated," Mr Debus said.

Gay rights groups who have long fought to have the age of consent for gay men lowered from 18 to 16 expressed their support for the move, noting that NSW is the last state in Australia to equalise the age of consent.

"I'm surprised that New South Wales has been so slow to move on this issue. It's renowned for public events like the Gay and Lesbian Mardi Gras but it is the last state in Australia to equalise the homosexual age of consent with the heterosexual one," the New South Wales Council for Civil Liberties president Cameron Murphy said.

Robert McGory, the convenor of the Gay and Lesbian Rights Lobby, believes there is widespread public support for lowering the age of consent.

"A lot of the research shows an unequal age of consent offers no benefit and is actually harmful to young gay men in inhibiting their access to educational and health and welfare services at a time when they need them the most," he said.