Councillors in Argyll and Bute have unanimously approved the plans for Loch Etive submitted by Alastair Salvesen's Dawnfresh Seafoods.
Mr Salvesen had led a doorstep campaign in the community to gain support for the bid by his firm, which supplies products to supermarkets and other retailers.
He made a series of unannounced visits to local residents to gather support for the plans Mr Salvesen is chairman of the Glasgow-based firm which is now expected to go ahead with the building of a new 10-cage site on the loch.
Members of the planning committee faced accusations of ignoring local interests by the Friends of Loch Etive campaign which opposed the development.
A spokesman: "Despite a persuasive presentation from Ardchatten Community Council, a powerful legal challenge by us and a series of strong arguments against, the councillors ignored all the protest and huge local opposition to the plan. So much for local democracy."
The committee's chairman, Councillor David Kinniburgh, said their views had been considered.
He added: "A lot of the concerns were related to the visual impact of the proposed fish farm, but the committee undertook a site visit last week and determined the project would pose no such risk. It is an expansion of the fish farm, but I certainly wouldn't call it 'industrialisation of the loch'."
Dawnfresh currently operates five fish farms on the loch, with the proposed site expected to the largest.
After the application was approved, opposition groups criticised the council for ignoring local interests.
Friends of Loch Etive said 89% of residents they had polled objected to the application.
No-one from Dawnfreshwas unavailable for comment.