Union leaders told Labour and the SNP to quit squabbling and work together to help save Clyde shipyard jobs amid accusations the Conservatives are pushing for posts to move to England.

Gary Smith, the GMB Scotland secretary, said: “We do not need point scoring between Labour and the SNP. The Clyde is not a political football.”

He added: “BAE is under pressure to move jobs to support Tory votes in the south west of England and help George Osborne’s 'Northern Powerhouse’".

Unions warn that up to 800 Clyde workers could be made redundant as a result of delays to a contract to build eight Type 26 warships for the Royal Navy.

The GMB union had threatened to allow the UK Government's flagship £6bn aircraft carriers, also being built on the Clyde, to rust if just one worker is put out of work.

The union has also accused the Scottish Secretary David Mundell of lying to workers about the future of shipbuilding jobs on the Clyde.

Earlier this week Mr Mundell said that shipbuilding jobs on the Clyde would be guaranteed “for years to come”.

In a letter to Mr Mundell, Mr Smith accused him of being disingenuous and “at worst” lying to workers.

SNP leader Nicola Sturgeon has called for a “cast-iron commitment” from David Cameron to deliver the contracts.

UK government sources rejected claims of pressure for jobs in Scotland as “utter nonsense”.

Earlier this week defence minister Philip Dunne said that ministers remained committed to building eight frigates on the Clyde.

But he refused to rule out redundancies as the result of delays.

The contracts were first promised in the lead up to the Scottish independence referendum, leading to claims of "betrayal" from SNP MPs.