The Ministry of Defence has been forced to restart its competition to build a fleet of five new frigates.

The MoD insisted it still wants the first of the ships - which each cost around £250m - delivered in 2023.

But the GMB union said the news was a blow to shipbuilding communities and the Scottish National Party described it as "utterly shocking".

The process to build the frigates is being restarted due to "insufficient compliant bids" being received for an "effective and robust competition", according to the MoD.

A spokesman said: "There have been no changes in our plans to procure a first batch of five new Type 31e frigates to grow our Royal Navy.

"We still want the first ship delivered by 2023 and are confident that industry will meet the challenge of providing them for the price tag we've set.

"This is an early contract in a wider procurement process, and we will incorporate the lessons learned and begin again as soon as possible so the programme can continue at pace."

Gary Smith, Scottish secretary of the GMB union, said: "This will come as a real blow to shipbuilding communities in Scotland and across the UK.

"We are already losing jobs in yards like Rosyth as the carrier work is completed.

"This news comes after big cuts to the original Type 26 programme, the broken promise to build a state of the art frigate factory on the Clyde that would have allowed us to compete in global markets for building complex warships, and the decision by the Tories to put the tender for the three support vessels for the carriers out to international tender as opposed to putting the work into UK yards.

"It is an utter shambles but this is what happens when you have Treasury dominating decisions over sovereign defence capability."

SNP defence spokesman Stewart McDonald added: "The MoD has been unable to answer the most basic questions about the cost of this new Type 31e frigates and today they have had to own up to their own chaotic failures."