A Ryanair boss warned Spanish cabin crew there would be "serious consequences" if they refused to operate flights during a strike by their Portuguese counterparts.

In a series of telephone conversations with anxious staff, head of human resources Darrell Hughes urged a group of flight attendants to ignore pressure "from other people" on social media and to "undertake" their duty.

The leaked recordings, obtained by the Irish Independent, offer a unique behind-the-scenes view of how Ryanair is tackling the disruption, which comes after the carrier's decision in December to recognise unions for the first time in its 30-year history.

Speaking to a Spanish group called up to replace Portuguese crew, Mr Hughes said the airline would not "tolerate any messing".

He said: "You guys do not have the legal protection to participate in this strike because you are not based in Portugal."

Mr Hughes stressed: "There is no legal basis upon which you can refuse to operate this duty".

He said he had given the crew the reassurance that "we will deal with any legal issues" arising out of Spanish staff operating flights during the Portuguese strike, although he emphasised Ryanair did not believe there would be any legal consequences.

But Mr Hughes warned staff there would be serious consequences if they did not carry out their duties: "This is the equivalent of just deciding you are not going to show up for work for some day with no valid reason."

Portugal's SNPVAC union is in the midst of a three-day strike, targeted at the Easter break. The action was carried out yesterday and on Thursday. A final day is planned for Wednesday, with the union blaming the move on below-par labour conditions. Ryanair says that its conditions are comparable to competitors.

In a statement to this newspaper, a spokesperson for the airline said "the vast majority" of its Portuguese crews were working normally yesterday.

They added: "A small number of first wave flights from Portugal were cancelled or suffered minor disruptions and these customers are being re-accommodated onto other flights."

Ryanair apologised to customers affected by delays "caused by this unnecessary and unjustified industrial action. We are grateful to our Portuguese crews for putting our customers first and largely ignoring this strike."

The spokesperson said Ryanair does "not comment on discussions with our people or rumour or speculation".

The calls, however, reveal some staff were concerned at operating flights during the industrial action. Mr Hughes assured crews that Ryanair would provide accommodation and meals "to make things as comfortable as we can".

But when asked to provide an email or letter to cover for any possible legal actions, Mr Hughes said: "Look, guys, we don't have time for sending emails or writing letters. I am giving you an absolute guarantee now that if there is any legal action taken against you individually, Ryanair will take over that case and Ryanair will fund the defence of that case."

Irish Independent