Island councils have joined forces to call for further powers to run their own affairs regardless of the outcome of next year's independence referendum.

Shetland, Orkney and Western Isles authorities want greater revenue-raising powers, improved energy connections with the mainland and a stronger recognition of their "status" in a Scottish constitutional settlement.

A key demand is for control of the sea bed, allowing revenue to be redirected from the Crown Estate to local needs.

New tax powers could give islanders more revenue from renewable energy and fisheries.

The three island council leaders set out their ambition in a joint campaign called Our Islands Our Future, hoping to build on the debate about Scotland's place in the United Kingdom.

Orkney Islands Council convener Steven Heddle said: "It is a measure of the importance of this to our three communities that we've joined forces today to ensure the voice of the islands is heard loud and clear during the pre-referendum debate.

"Islands by their very nature are special places with special requirements. The Western Isles, Shetland and Orkney each have a strong sense of identity. What we share is an abundance of natural resources and a pride in our cultural traditions.

"What we are calling for is a commitment that whatever the outcome, the needs and status of island areas are clearly recognised in the new era for Scotland that follows the referendum."

Angus Campbell, leader of Western Isles Council (Comhairle nan Eilean Siar), said it represents a once-in-a-generation opportunity for the islands.

"The constitutional debate offers the opportunity for the three island councils to secure increased powers for our communities to take decisions which will benefit the economies and the lives of those who live in the Islands," he said.

"We look forward to making that happen by working together as islands with the Scottish and UK governments."

Shetland Islands Council leader Gary Robinson said he wants to strengthen existing governance.

"There's no doubt that this is an historic opportunity for the islands, which will continue to punch above their weight in terms of their economic and cultural contribution to Scotland," he said.

Tavish Scott, the Liberal Democrat MSP for Shetland, backed the island councils' plan.

Scottish Lib Dem party activists have already agreed that Shetland and Orkney should loosen ties with Scotland and the UK and that the islands have a separate right to self-determination.

Mr Scott said: "London is pretty remote from our Islands. When the Scottish Government spend every working day removing power, financial and policy responsibility from local people a stand must be taken.

"I am very pleased that the island councils have now produced a blueprint of what they want from their governments. Devolution on power in 1999 to the Scottish Parliament in Edinburgh from London was meant to be about enhancing local government. Sadly the experience has been the opposite."

Scottish Conservative deputy leader Jackson Carlaw said the islands present an interesting argument but they cannot expect "better treatment" than any other area.

"Devolution has to work both ways, but the SNP's brand of it wants power from both sides," he said.

"Alex Salmond is intent on getting all the power he can from Westminster, and at the same time grabbing power from councils and other localised organisations. He has to realise you can't devolve on one side and centralise on the other.

"These councils have set out an interesting argument and while they can't expect to receive better treatment than any other area of Scotland, it is a welcome addition to the debate.

"We are all for councils being more accountable to those living in the area they serve. On many issues, there is no better decision-making body than the local authority."