Bob Brown, the leader of the Australian Greens has announced his resignation as his party’s leader and a senator in the Canberra federal parliament.

Mr Brown, 67, said he was “very sad to go but very happy to make way for the depth of talent” in the Greens after 16 years as leader, the Sydney Morning Herald reports.

As leader of the party, which occupies one of 150 seats in the House of Representatives and nine of 76 in the senate, Mr Brown has long called for full marriage equality for Australian gay couples.

Senator Christine Milne will take over as leader. She said: “Under Bob’s wise leadership, the Greens have grown into the undisputed third force in Australian politics, with our vision, policies and action towards a healthier, cleverer, cleaner future embraced by 1.7 million Australians.

“Under my leadership, we will work tirelessly towards making Australia a great place to live and work.

“For 25 years, Bob has been an inspiration to millions of Australians and a great force for good in our country. But he’s also been a colleague, a mentor and friend to me. I thank him from the bottom of my heart for everything he has done and look forward to the next stage in his career.”

Tasmanian Gay and Lesbian Rights Group spokesperson, Rodney Croome, said Senator Brown had been an important role model for the island.

He said: “Bob Brown’s charm, erudition, bravery and compassion, and most of all his pride in being gay in face of deep prejudice, have made him a beacon for three generations of gay and lesbian people in Tasmania and across the nation.

“All of us owe Bob a debt of gratitude for the rights we have, for the acceptance we enjoy, and for the hope we have of a better future.”

Of Senator Christine Milne’s appointment as the new Australian Greens leader, he said: “In my long experience working with Christine Milne I have found her to be one of the nation’s most effective, fearless and dedicated advocates for gay, lesbian, bisexual and transgender equality.”

“It was Christine Milne whose legislation finally removed criminal laws against homosexuality in Tasmania, and I’m hopeful it will be under Christine Milne’s leadership that Australia will achieve marriage equality.”

Senator Brown was the first openly gay member of Australia’s parliament and the first openly gay party leader.

Prime Minister Julia Gillard said his political career was characterised by passion for the environment, but added he has “also been an active voice on the rights of same sex couples, having bravely used his own experiences to campaign for change.”

Senator Brown said he looked forward to “writing, photography, music, occasional talks, bushwalking, and getting out with [his partner] Paul to see Miranda Gibson who has been perched for 120 days 60 metres high, in defence of a giant tree facing destruction in central Tasmania.”