P&O Cruises Southampton's entire fleet of superliners could be put up for sale if Carnival Corporation, the world's biggest cruise company, takes control of the city-based company.

"For Sale'' signs are set to be slapped on Aurora, Oriana and Arcadia although Victoria is already earmarked to leave P&O later this year.

P&O has only recently announced it would be boosting its Southampton operation by bringing two further superliners, Oceana and Adonia into service later this year and in 2003.

If any of these ships were to be sold and moved away from Southampton it would hit the local economy hard as P&O Cruises' vessels play a vital role in the port's huge cruising industry.

At the same time Cunard, with its European headquarters in Southampton, has been assured that it has a safe future in the port within the Carnival Corporation empire.

This is the latest dramatic twist in the long running and highly complex takeover bid by Carnival to gain control of P&O Princess Cruises which has already announced it would prefer a merger with another company, Royal Caribbean Cruises.

A spokesman for P&O Cruises said the company had nothing to say at this stage while awaiting any decision from the regulatory authorities.

There had been earlier suggestions that Carnival, with Cunard within its stable of companies, would consider selling the operator of Southampton's Queen Elizabeth 2, in order to receive regulatory clearance in Europe for its proposed bid to acquire P&O Princess.

This has been totally denied by Carnival but it has now said selling off P&O Cruises' UK ships would be considered.

"Cunard has currently two new vessels under construction - the 150,000-ton gross-registered Queen Mary 2, which will be the world's largest passenger ship and the first transatlantic liner constructed in more than three decades, and an as yet unnamed 85,000-ton vessel scheduled for delivery in January 2005," said Carnival in a statement today.

"These two vessels represent a $1.2bn investment in the future of Cunard Line and demonstrate Carnival's full commitment to expanding this world-recognised brand.

"However, should it ultimately prove necessary, Carnival would, in certain circumstances, be prepared to consider disposing of P&O Cruises."

The 69,153-ton Oriana was officially named by the Queen and entered service in Southampton in April 1995 and has become one of the most popular ships in the rapidly-increasing British cruise market.

The Princess Royal named the 76,000-ton Aurora in a Southampton quayside ceremony in May 2000 and since then the ship has become a familiar sight on the city's skyline.