The 143,000-ton, 3647-passenger ship, which comes into service in March next year, was officially blessed by a local priest before a ceremonial bottle of prosecco was smashed against its hull by the 'Madrina' -- UK travel agent Louise Hunt.
It is the fifth P&O ship built at the shipyard and the 62nd Carnival-owned ship.
Pre-registration for the maiden cruises on Britannia opened yesterday and generated more calls in one day than in the first week that cruises on P&O's last new build, Azura, went on sale in 2010, according to Carnival UK's chief commercial officer Gerard Tempest.
"It's contemporary and sophisticated, mixed with the enduring hallmarks of P&O Cruises," he said at the ceremony, which included the P&O's UK head Christopher Edgington, the head of the shipyard, Giuseppe Bono, the ship builders, media and travel agents.
"High quality food, service and entertainment, delivered with style and glamour."
Tempest emphasized that the ship was very much built with passengers in mind:
"We asked what passengers wanted and they said single cabins with balconies – Britannia will have that.
"They wished for more choice of dining – Britannia will certainly have that, with 13 dining options. There will also be more shopping, more entertainment and the biggest spa in the fleet."
P&O revealed details of the ship's stand-out features at an event on Wednesday (February 12), which will include the UK's first onboard cookery school run by celebrity chefs including James Martin, Marco Pierre White and Olly Smith.
The line also confirmed Britannia's maiden voyages which includes the Mediterranean, British Isles, the Canary Islands and the Caribbean.
--by Adam Coulter, UK Editor