Renewed fears over the future of Longannet and its 260 jobs have emerged.
Last year ScottishPower warned the Kincardine plant was not on a level playing field to compete with those in the south.
Keeping the coal-fired station connected to the national grid costs £40 million a year while those in the south make a £4m payment to stay linked.
That was why ScottishPower made the decision not to enter Longannet into an auction for delivering electricity generating capacity for the winter of 2018/19.
At that point boss Neil Clitheroe said to avoid closure “within the coming years” changes to the plant’s financial situation must be achieved.
It has now been rumoured that talks have stalled and Longannet, which plays a pivotal role in keeping the power network safe and stable, may close earlier than planned.
A ScottishPower spokesman said: “We are concerned about Longannet and are currently doing all that we can to guarantee the future of the power station as it plays an essential part of the energy system in Scotland.”
Meanwhile, following a meeting of the Scottish Energy Advisory Board, First Minister Nicola Sturgeon has written to David Cameron urging him to order an assessment of Scotland’s electricity capacity.
Ms Sturgeon has asked the Prime Minister to call for an analysis of electricity capacity margins in Scotland and to seek reassurance that the UK Government understands the key role which Scotland plays in ensuring adequate levels of energy security across the UK.
“These issues need to be assessed,” she said.