The entire fleet of the Royal Navy's most advanced warships are currently in port and not on operations, the Ministry of Defence has confirmed.

A photograph showing the vessels docked in Portsmouth was published by the website UK Defence Journal.

A source told Sky News that the ships had either "just got back from operations, are about to go on operations, or are having planned maintenance done".

But another senior figure said it was "almost unprecedented" that all the ships should be in port and "it either showed a gross lack of planning or was indicative of something more serious".

The Type 45 Destroyers are primarily designed for an air defence role.

Their advanced radars are capable of scanning the skies to detect and engage enemy aircraft. But recently the fleet has experienced serious engineering issues.

This is the latest embarrassment to beset the fleet.

All six ships, worth £1bn each, need to be refitted with new engines after some of them broke down.

This work is due to begin in 2019 and the MoD has guaranteed it will not affect operational capabilities.

It will put a further strain on the Royal Navy, which has been considerably cut in size in recent years, and it will put into doubt the safety of the new aircraft carriers which will rely on the Type 45s for security.

A Ministry of Defence spokesperson said: "This week the Royal Navy had over 8,500 personnel deployed on operations around the world and 34 ships at sea.

"All Type 45 Destroyers are currently in port as they have either just returned from operations, or are about to be deployed, are conducting training or carrying out maintenance or are home for crew to take summer leave."