A trade union has urged politicians to stop treating the troubled Longannet power station like a "political football" and work together to secure its long-term future.

Last week, it emerged that the Fife plant will close by the end of March next year unless owner Scottish Power secures a short-term contract with the National Grid to help maintain voltage levels in the electricity supply.

Deputy First Minister John Swinney visited the plant yesterday (mon) and blamed the current crisis on UK energy policies which saddle Scottish generators, which provide 12per cent of the UK's energy supply, with "35per cent of the charges".

But Conservative energy spokesman Murdo Fraser blamed Longannet's woes on the Scottish Government's "obsession" with wind power.

Prospect, the union representing engineers and professionals in the energy supply industry, will meet with shadow energy minister Tom Greatrex today to urge him to push for a deal on the National Grid's regionally-based charging system, which "discriminates against electricity generation in Scotland".

Prospect negotiator Richard Hardy said: "It's important that politicians stop using our members as a political football.

"This issue is about jobs and the ability of all companies to develop new generation assets for Scotland.

"It shouldn't just be seen as an opportunity to back one of the 'Big Six'."

Mr Swinney said: "This situation illustrates why Scotland must no longer accept a position where our levels of electricity security are threatened by UK energy policies.

"National Grid say that proposed changes will reduce charges by one-third but Longannet's charges are forecast to increase from £40 million this year to £51 million in 2017 and 2018.

"That is why Longannet is threatened with premature closure and why jobs and investment are being lost to Scotland under the current UK regime."

Mr Fraser, convener of Holyrood's Energy Committee, said: "The Scottish Government are right to be concerned about security of energy supply but it is their obsession with developing vast amounts of intermittent and expensive wind energy that have contributed to the current situation."

Neil Clitheroe, chief executive of retail and generation at Scottish Power, replied: "Our plan was always to get to 2020 and keep this plant going.

"We've invested £350 million in the plant over the last six or seven years."