Tavish Scott has called on Shetland and Orkney to have home rule separate from the rest of Scotland.
The Shetland MSP said the isles should have a right to self-determination when he addressed the Scottish Lib Dem conference in Dundee on Saturday.
A motion proposed by Mr Scott, and backed by his Orkney counterpart Liam McArthur before being unanimously passed by the party, insisted the two island groups should be able to determine their own future.
Mr Scott insisted those who cared most about the Northern Isles were those who lived there. The burden should rest on their shoulders, he said, to decide their future.
The call comes ahead of an anticipated statement by First Minister Alex Salmond in the Scottish Parliament on Thursday, when the date of next year’s Scottish independence referendum is due to be confirmed.
One possible outcome of any constitutional change could be a self-governing crown dependency, similar to the Isle of Man.
Mr Scott said: “The Northern Isles are vibrant, distinctive, with our own dialect, language and Norse festivals. Orkney and Shetland both fly their own flags. Our history looks east more than south.”
“That is my point; Shetland and Orkney want to use this period of intense constitutional navel gazing to decide what we want. We are not going to be told what to do by the SNP, nor by any other government. This is the time to seize the opportunity of island home rule.
“We don’t want more centralising, know-it-all, top down nationalism. This SNP government couldn’t care less about the outer extremities of the country – they’ve centralised our police and fire services, left crofting law in shambles and removed support for vital air links to the islands.
“What next? Those who care most about the future of the Northern Isles are those who live there, and they should decide their future.
“If that mantra is good enough for Salmond and Sturgeon it is certainly right for Scott and McArthur.”
Mr Scott insisted SNP plans to take billions of pounds in tax revenues from North Sea oil were premature – not least, he said, because Shetland had a say in the future of the much-valued reserves.
“Two thirds of the North Sea and west of Shetland reserves are in Shetland coastal waters. The Northern Isles don’t need nationalists negotiating Scotland’s oil share, it’s wirs. We have plenty of our own leverage.
“Shetland and Orkney may never have a stronger opportunity to negotiate a future for the islands.
A future that benefits the economy, culture and our identity in the wider world for the advantage of future generations of islanders.”