A cruise in a liner officially named this summer by the Duchess of Cambridge has had to be curtailed after the vessel lost power.

And the next voyage of the ship - the Royal Princess - is now in doubt.

The Duchess named the ship, part of the Princess Cruises fleet, in a ceremony at Southampton in June - one of her last engagagements before the birth of her son George the following month.

The ship suffered a power outage while sailing in the Mediterranean between Mykonos and Naples this week.

Although the power was restored, the ship needs to be taken to Barcelona for repairs.

Passengers will be taken to Naples for flights home and the ship will leave tomorrow for Barcelona with only crew on board.

The Royal Princess is due to embark on a 30-day cruise on Friday, finishing in Fort Lauderdale, Florida.

A spokeswoman for Princess Cruises said: ''We sincerely regret this means the remainder of the current cruise will be cancelled, and passengers will disembark the ship in Naples.

''Passengers will be provided a full refund of their cruise fare, along with a 25 per cent future cruise credit.

''We have dispatched a care team to Naples to ensure that all our passengers are provided with any assistance they may require.

''The impact of the repairs on the next Royal Princess cruise, scheduled to depart from Barcelona on September 27, is not yet known and we will keep passengers fully advised as details become known.''

Royal Princess arrived in the Italian port of Naples last night to be met by a team of engineers who immediately went on board to assess the problem and start work on repairing the engine.

Repair work will continue after sailing from Naples on Wednesday, and en route to Barcelona. The impact of the repairs on the next Royal Princess cruise scheduled to depart from Barcelona on Friday, September 27, is still being evaluated.

“We fully appreciate that booked passengers are eager to know the status of this sailing, and we plan to provide these details early this afternoon,” said a Princess Cruises spokesman in Southampton. Princess' shore team has continued to arrange flights within the next few days and secure hotel rooms for those who will require an overnight stay prior to their onward flights.

The spokesman said: “Once again, we are deeply sorry for this unanticipated disruption of our passengers' holiday plans, and we appreciate their patience and understanding of these circumstances.”