The Scottish Government could be forced by law to devolve more power to the northern and western isles.
Liberal Democrat MSPs Tavish Scott and Liam McArthur are introducing a private members bill to parliament to force SNP ministers to keep promises they have made to people in Orkney, Shetland and the Western Isles.
They said they wanted to ensure the government did not “backslide” on its commitments, regardless of the referendum result.
Mr Scott, MSP for Shetland, claimed SNP ministers could devolve extra powers to the three local authorities right now.
First Minister Alex Salmond has pledged to give all island communities 100% of net income yielded by the Crown Estate to fund services and projects as they saw fit if people vote yes.
He has promised they would have a stronger voice in Europe, additional support would be given to beef farmers, and innovation zones would be set up to sustain job opportunities.
Mr Salmond said all public bodies would have a duty to “island-proof” their functions and decisions to make sure they meet local needs and the government would create a post of Minister for Island Communities.
The Lib Dems MSPs will publish a public consultation paper on their proposed bill after the referendum.
It will examine community benefit in areas such as aquaculture; fisheries management, relocation of posts, islands innovation zones and consider steps to protect lifeline air and ferry provision.
Mr Scott said: “SNP ministers have been busy making all sorts of promises in a bid to persuade islanders to vote for independence.
“In most cases, however, there is nothing stopping the SNP from delivering these promises now.
“I don’t want to see the nationalists backsliding after September 18 and this bill should help make sure this doesn’t happen.”
Mr McArthur, MSP for Orkney, said the three island councils have said their demands for change were not linked to a particular outcome in the referendum.
“Yet the SNP have refused to listen, insisting that they are only interested in giving islanders what they what, if they get what they want in return,” he added.
“That is not on, particularly given the centralisation of power we have seen under the nationalists over recent years.”
The opposition MSPs expect the UK Government to also keep promises made to islanders in the event of a “no” vote but have no legislative influence over Westminster.