The Scottish Government made the new commitment at a meeting with the leaders of Orkney, Shetland and Western Isles councils.
It is a further boost for their campaign, which was launched earlier this year, to enable the islands' councils to decide their own futures. It aims to increase their authority regardless of next year's poll result.
Ministers launched the Island Areas Ministerial Working Group to work with the councils and its third meeting was held earlier this week. Chairman Derek Mackay, the minister for Local Government and Planning, said: "The best prospect of implementing the outcome of the group's discussion is with the full powers of independence, and in that event we propose to bring forward a bill for an Islands Act."
Steven Heddle, convener of Orkney Islands Council said: "The three islands' councils maintain their position that there should be legislation within the lifetime of this parliament regardless of the outcome of the referendum while also respecting the political position of the Scottish Government."
Richard Lochhead, Cabinet Secretary for Rural Affairs & the Environment, Fergus Ewing, Minister for Energy, Enterprise & Tourism, and Paul Wheelhouse, Minister for Environment & Climate Change, were all also in attendance at the meeting.
The councils' aspiration to control of the seabed around their islands, which would allow revenues that are currently paid to the Crown Estate to be channelled into local causes, was discussed.
The leader of the islands' councils are also in a continuing dialogue with the Scottish Secretary Alistair Carmichael.