DEPUTY First Minister Nicola Sturgeon has warned warring politicians to put aside their differences and show a united front in the battle to save thousands of threatened shipyard jobs on the River Clyde.

Her intervention followed politically charged responses to BAE Systems chief executive Nigel Whitehead's admission that the defence giant is considering closing one of its three major yards.

Mr Whitehead's announcement puts Govan and Scotstoun, which have a combined workforce of about 3500, into a battle for survival with Portsmouth. The south coast yard has an estimated 5000 workers, but less than 50% are directly involved in shipbuilding.

With the referendum on Scotland's independence due in autumn 2014, Ms Sturgeon, who is MSP for Govan, said: "BAE Systems is a hugely important employer in Scotland, and we want to ensure that the strongest possible case

for the retention of the Scottish yards is made and acted upon.

"Scotland showed during the Strategic Defence and Security Review an ability to put political differences aside and unite in the Scottish interest – and I believe the same constructive and positive approach is needed now."

She insisted that Scotland's yards were in a strong position because of their excellent industrial and engineering capability.

She added: "The Scottish Government is monitoring this situation closely, and will work with BAE, the UK Government and opposition parties in Scotland with the clear aim of ensuring that any future plans protect Scotland's shipbuilding yards and the highly skilled jobs that depend on them."

Labour's Shadow Defence Secretary Jim Murphy stoked the fires of a constitutional battle when he appeared to side with Portsmouth.

Mr Murphy said: "Why keep open two yards that could potentially be in a foreign country by 2016?

"If I was in Portsmouth I may say, look, you are the only yard that is guaranteed still to be in the UK come 2016, so why would you shut the one yard that is still going to be in the UK?

"I think that is the strongest card that they could be playing over the next few days."

He later added: "Scotland has got to come together to see off the immediate threat of a shipyard closing, but by 2014 we need to come together again to take on the real long-term threat to Scottish shipbuilding, which is leaving the UK and making the Royal Navy a foreign service."

Portsmouth City Council leader Gerald Vernon-Jackson said: "It would be disappointing to see shipbuilding stop in Portsmouth.

"It's wrong for Britain because it means all advanced naval shipbuilding will be in Scotland, and what happens if Scotland becomes independent?"