Ryanair has been referred to employment and tax authorities for investigation by two parliamentary committees, citing the airline’s “refusal to cooperate” with inquiries over crew pay and conditions.

Frank Field, chair of the work and pensions committee, and Rachel Reeves, chair of the business select committee, have written to HMRC and the director of labour market enforcement asking them to investigate Ryanair and the agencies that supply its cabin crew.

Late last year, Ryanair declined to answer further questions about pay and employment practices, after an initial response failed to satisfy MPs.

The committees sought more information after reports that cabin crew were required to work for free, pay for training and uniforms and take significant periods of unpaid leave, which suggested that agency workers were receiving less than the living wage.

A letter from Ryanair’s HR director, sent on 21 December, said crew earned between €24,000 [£21,150] and €40,000 [£35,250] a year, double the legal minimum for the work carried out.

However, MPs said that the letter ignored many of their questions while the pay figures did not tally with a contract they had seen.

Field and Reeves have told HMRC and Sir David Metcalf, the government’s director of labour market enforcement, that despite Ryanair’s assurances, it appeared that cabin crew were being paid in a confusing and opaque way, that could mask low pay and poor conditions.

They wrote: “We believe it is vital that potential poor employment practices are examined not only to ensure the rights of Ryanair cabin crew are protected, but also to ensure that there is no ‘race to the bottom’ across the aviation sector.”

Field said: “We and the public can draw our own conclusions about Ryanair’s comprehensive failure to answer allegations on its pay and employment practices.” They had requested that HMRC extend its current investigation into Ryanair pilots to look at cabin crew, he said.

Reeves said she hoped that HMRC would look at the airline’s practices as a matter of urgency. “Ryanair might want to dodge our committees’ questions and hide behind excuses, but the UK is the largest provider of workers to the company and we must be sure that everyone working for Ryanair is receiving fair pay and reasonable working conditions.”

A spokeswoman for the airline said: “Ryanair has already confirmed to this committee that its pilots earn between €130,000 [£114,550] and €180,000 [£158,600] per annum and our cabin crew between €24,000 and €40,000, which is more than double UK national minimum wage, and since we also comply fully with UK employment law, we have no further comment in response to this committee’s inaccurate press releases.”

Earlier, the airline said that pilots across its 15 UK bases had voted to accept pay increases of up to 20%, while talks continued with British pilot union Balpa over recognition.

Talks with Irish unions are also continuing, after the airline announced last month it would reverse previous policy and recognise unions.

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