Eighty per cent of rental properties in the Western Isles do not meet a proposed new energy efficiency standard, a TV investigation has found.

However, the islands are ranked joint third with the Borders, behind only Dumfries and Galloway on 81% and poll toppers, Shetland as the worst performing local authority area with 83% of rentals failing the new standard.

The Scottish Government plans to introduce new regulations in 2025 that require all privately rented properties to achieve a minimum standard equivalent to an EPC C rating, where it is “technically feasible and cost-effective” at the change of tenancy. All remaining existing properties have until 2028 to meet the energy benchmark.

Those properties falling short are graded with an EPC rating of D or lower.

The BBC’s shared data unit analysis reveals that more than half of the rental properties recently inspected Scotland-wide would fail the new energy efficiency test. Assessors also concluded that around six per cent of the properties inspected did not have the potential to be upgraded.

The data means Scotland-wide, tens of thousands of private rentals require extensive energy efficiency improvements to meet the regulations coming into force in two years.

Also uncovered was the extent to which tenants rely on a secondary heating source such as portable heaters.

In the Western Isles and Orkney, 69% of tenants have a backup heating source.