Strikes at Scottish nuclear plants could lead to power shortages over Christmas, a union has warned.

GMB has threatened industrial action at Hunterston B and Torness, which it says could leave Scotland without a third of its electricity supply.

Union members are locked in a dispute with EDF Energy over pay and contracts.

Contingencies would likely be put in place to keep the electricity grid running if strikes were to go ahead over Christmas.

GMB says it has informed the Scottish Government about the implications of industrial action at the two sites, which employ a total of 1500 workers.

GMB Scottish secretary Gary Smith said: "Industrial action at Hunterston B and Torness could have profound implications for electricity generation and supply across Scotland but we have been left with little choice than to take on EDF over these draconian cuts.

"Outages are a statutory requirement, a safety-critical process delivering the maintenance of our nuclear reactors.

"During these periods staff become fully available, work flexibly to accommodate the employer's requirements and receive enhanced rates in return."

The dispute centres on EDF's plans to cut a long-standing agreement about pay and contracts during outages.

GMB intends to launch a consultative ballot on industrial action on October 16.

"It is ludicrous that a hugely profitable multi-national like EDF is trying to break this agreement," Mr Smith added.

"This is not a decision we are taking lightly, but we hope that EDF will see sense."

EDF Energy said it had not formally been made aware of the union's plans.

She added: "We're sharing open and constructive dialogue in a period where costs are going up and income from electricity generation is going down and have been having productive conversations on how to achieve our shared goals."