A leading cruise ship operator has strongly denied claims it is planning to threaten hundreds of crew with being fired and rehired if they do not accept reduced terms and conditions.

The Nautilus union said Carnival UK has told authorities in the UK and Bermuda of its intention to change employment terms and conditions for 919 crew across 10 of its vessels.

Crew on the affected fleets includes those on P&O Cruises and Cunard, on ships such as the Queen Elizabeth and Queen Mary 2, the union said.

P&O Cruises is separate to P&O Ferries, which was embroiled in a row over the sacking of hundreds of workers.

The company said in a statement: “We are categorically not making any redundancies and we will not dismiss and re-engage staff.

“In fact we have significantly increased our headcount across our fleet. This is an annual pay review process with our maritime officers onboard our ships which will ensure alignment.

“This will empower our staff, deliver the right teams across our fleet and attract and retain talent to work on our ships.”

TUC general secretary Paul Nowak said: “After last year’s P&O Ferries scandal – when 800 staff were brutally sacked without notice – the Conservatives promised to clamp down on rogue bosses.

“But ministers have not lifted a finger since to strengthen employment law and stop workers from being treated like disposable labour.

“This appalling episode should never have been allowed to happen. It shows that you can’t trust the Tories with workers’ rights.”