PM says thanks to retiring navy ship

Prime Minister Tony Abbott has paid tribute to HMAS Tobruk, the navy's ageing amphibious supply ship who made her final voyage into Sydney Harbour on Thursday ahead of decommissioning.

Mr Abbott said after 34 years, Tobruk and her crew had served Australia with distinction, supporting a series of defence operations, most recently disaster relief in Vanuatu.

"HMAS Tobruk has fulfilled her mission and a grateful nation says thank-you," he told parliament.

Named after the World War II siege in which Australian troops played a heroic part, Tobruk was constructed at the Carrington shipyard in Newcastle and commissioned into the navy in 1981.

Opposition Leader Bill Shorten said Tobruk had given fine military and humanitarian service to Australia and our region.

"She has done her duty faithfully and well and we thank her," he said.

Even House of Representatives Speaker Bronwyn Bishop commented on the sad occasion.

Harking back to her days as junior defence minister in the Howard government, Ms Bishop said Tobruk was due to be retired 20 years ago.

But the navy managed to persuade her and then defence minister Ian McLachlan that they couldn't do without her.

"It is with a sense of sadness that I see her being paid off now," Ms Bishop said.