Royal Caribbean International will get a fifth Oasis-class ship while Celebrity Cruises will get a further two Edge-class ships, to go with the two already on order.

"The response to the arrival of Harmony of the Seas is staggering, eliciting excitement from eager cruisers from markets on both sides of the Atlantic," said Richard Fain, chairman and chief executive, Royal Caribbean Cruises.  "And Edge-class is one of the most highly anticipated new projects, following the high bar of Modern Luxury design set by its predecessor, the Solstice-class."

Royal Caribbean’s third Oasis-class ship, Harmony of the Seas, arrived in Southampton for a preview sailing last week. A fourth ship in the same class is due to be delivered in 2018.

Celebrity Cruises first two Edge-class ships are due to be delivered in 2018 and 2020.

"Although our first Edge-class vessel is still over two years away from delivery, there has been a tremendous amount of interest around the new standard of style [it] will introduce," said Lisa Lutoff-Perlo, president and chief executive of Celebrity Cruises.

The new order follows the signing of a memorandum of understanding with shipbuilder STX France.