A letter to the Scottish Government from council and development agency bosses said an estimated 300 jobs have been lost on the Western Isles.
Writing to Enterprise Minister, Jim Mather, Comhairle nan Eilean Siar and Highlands and Islands Enterprise (HIE) said the posts went within six months.
Comhairle leader Angus Campbell and HIE chairman William Roe signed the letter.
It has been sent ahead of the publication of a government report on the economic potential of the isles.
The letter outlines problems affecting the islands - such as the closure of the Lighthouse Caledonia fish processing plant, redundancies within Harris Tweed and the building industries.
Europe's largest
It goes on to tell how more should be done to capitalise on the emerging renewable energy sector - specifically from onshore wind developments.
In April, plans to construct one of Europe's largest onshore wind farms on Lewis, which it had been predicted would create 400 local jobs, was refused planning permission by the Scottish Government.
It said Lewis Wind Power's (LWP) 181-turbines did not comply with European law protecting sensitive environments.
The scheme had the backing of the comhairle and business, but attracted almost 11,000 objections.
Scottish ministers decided the project would have a serious impact on the Lewis Peatlands Special Protection Area, which is designated under the European Commission (EC) Birds Directive and protected under the EC Habitats Directive.
At the time, Mr Mather said the government was committed to helping the renewable energy sector in the Western Isles.
The letter comes ahead of publication of the government's economic and community benefit study.
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