THE Royal Navy’s most modern warships will need to have holes cut in their sides to fit them with new engines because they keep breaking down.

The Ministry of Defence (MoD) has confirmed that the six Type 45 destroyers, partly built in Scotland, are to undergo major refits amid concerns over their reliability.

The work will be staggered over  a period of years so some ships remain available for operational commitments at all times.

The move follows reports of persistent problems with the engines and power systems on the ships, which cost £1 billion each.

In 2014, HMS Dauntless had to abandon a training exercise and in 2009 HMS Daring lost power on her first voyage to the US.

Each of the ships, which are described as “part of the backbone of the Royal Navy”, are fitted with four engines – two gas turbines and two diesel generators supplying a system of integrated electric propulsion.

All four engines generate power to drive the ships’ electrical motors which turn the propellers. They also generate power for all other systems on board.

A Royal Navy source said the most likely action will be to add    two extra generators to each ship to “bolster the power that’s already there”.

The source said that carrying out such maintenance a few years into the ships’ service was not “normal”.

The MoD has not disclosed the cost of the work but it is thought that it could run to tens of millions.

Cutting in to the side is a normal way to access the engine rooms in the bottom of the ship, the source added.

“It’s perfectly normal practice for maritime maintenance,” he said.

An MoD spokesman said: “The Type 45 destroyers are hugely capable ships and have consistently made a difference to our safety and security.

“In our defence review last year we committed to improving the Type 45’s power and propulsion system through a series of machinery upgrades during planned maintenance, which will ensure increased availability and resilience over the life of the ships.”

BAE Systems, which built the ships, said it was “working collaboratively with the MoD and industry partners to deliver improvements to the power generation capability of the Type 45 destroyers”.

Rolls-Royce, which makes the WR-21 gas turbines, said they will continue to work with the MoD “on upgrading the performance of the propulsion system”, and Wartsila, which makes the diesel generators, said it is “co-operating with the Royal Navy and we are fully committed to support the customer in operating the engines efficiently”.

The MoD said: “The destroyers are used in hunting pirates, drug runners or submarines, defending the fleet from air attack, and providing humanitarian aid after natural disasters.”

Last year it was disclosed destroyers would be used as support and protection for the USS Theodore Roosevelt and Charles de Gaulle aircraft carriers as they carried out air attacks against Islamic State.

No decision has been made on where the work will be done.