Western Isles Council has raised concerns about the resilience of electricity supplies to parts of the Western Isles.
A subsea cable linking Harris with the mainland grid failed in October 2020.
Power had to be provided by back-up generators on the isles for 10 months before a new cable could be laid at a cost of £28m.
Local authority, Comhairle nan Eilean Siar, worries there could be a repeat of the problem with 30-year-old infrastructure that connects Uist and Barra.
Energy firm SSEN Distribution has plans for two new subsea cables, but regulator Ofgem has not approved the funding.
SSEN Distribution said it was “deeply disappointed” by the decision, adding that it was continuing to work with Ofgem to reach a positive outcome.
Ofgem said it had not rejected the case for new connections.
A spokeswoman added: “However, developers’ proposals must fully demonstrate how they meet what is required.
“We are currently consulting on future energy infrastructure investment for Uist and would welcome feedback from the community in Uist including any community-owned renewable energy companies.”
