The Ministry of Defence (MoD) has insisted it is "fully committed to operating" both new Royal Navy aircraft carriers following speculation over their future.

The statement comes after a shipbuilding union called for "urgent clarification" over reports that one of the carriers could be mothballed to help address a £500 million budget shortfall.

Workers at Rosyth in Fife and other yards across the UK are currently manufacturing the Queen Elizabeth Class carriers, HMS Queen Elizabeth and HMS Prince of Wales, and have commitments to maintain the vessels throughout their lifetime.

The GMB union said "alarm bells are ringing" among members at the suggestion future work could be reduced.

It follows a report in The Times that the Royal Navy is trying to save £500 million over the next two months after "wasting money on ships it did not need".

Other options suggested include cutting the size of the Royal Marines, and a failure to meet the budget shortfall would mean the Army, Royal Air Force and Joint Forces Command will be asked to bail the Navy out, the Times reported.

GMB Scotland Organiser Gary Cook said: "The mere suggestion that one of the aircraft carriers could be mothballed by the MoD will set alarm bells ringing among our members and particularly in Rosyth.

"A large chunk of the future prosperity of these yards are invested in the maintenance and routine refitting work associated with Royal Navy vessels and potentially cutting this work by 50% would have serious consequences for jobs.

"GMB is also campaigning to bring the manufacture of three Royal Fleet Auxiliary support vessels to yards across the UK and any impact on the future of QE class carriers would also call into question the future outlook for these orders too.

"Less than two months since the Parker Report spelled out the massive economic and employment opportunities for shipbuilding in the UK, it's deeply worrying that the MoD is flirting with proposals that could harm our shipbuilding communities.

"Such short-sightedness would be bad news for Rosyth, bad news for Scotland and bad news for the future of UK shipbuilding and we are calling on the UK Government to provide urgent clarification on these reports."

An MoD spokesman said: "We are fully committed to operating both HMS Queen Elizabeth and HMS Prince of Wales and to naval shipbuilding on the Clyde.

"The Defence Secretary confirmed last year that steel will be cut on the first anti-submarine Type 26 Frigate this summer, providing warship building work on the Clyde until 2035.

"Britain has the largest defence budget in Europe and it is growing as we invest £178 billion pounds in new ships, submarines and aircraft over the next decade."

HMS Queen Elizabeth is due to sail from Rosyth ready to conduct sea trials this summer.