NSW Premier Gladys Berejiklian has come out strongly in favour of support for same-sex marriage, describing it as one of the most important human rights issues "of our time".

Ms Berejiklian has previously indicated her support for same-sex marriage and recently attended the launch of an event for Liberal and National party voters who were voting 'yes' in the forthcoming national postal plebiscite on marriage equality.

But at a fundraiser event at NSW Parliament for Australians for Marriage Equality on Tuesday night she made her strongest public statement on the issue to date.

"I'm extremely proud to be here as the Premier of NSW," she said. "I'm hoping that all of us will look back and feel really proud that we were part of something special [and] putting aside our political differences in support of what is one of the most important decisions of our time in terms of human rights and social justice."