Ryanair has warned it could axe hundreds of UK flights if Rachel Reeves raises aviation taxes in her Budget.

Michael O’Leary, the low-cost airline’s chief, said that any increase in air passenger duty (APD) would hurt customer demand and undermine the viability of some routes.

This would spark inevitable cut-backs for Ryanair, he said, as he singled out the prospect of the Chancellor increasing APD on internal flights.

Mr O’Leary said: “If they raise APD again on domestic flights then there will be a cut in capacity, no question. These routes are not particularly profitable, they barely break even.”

His comments come after Ryanair slashed 12pc of its capacity in Germany in protest against higher taxes. The move demonstrated the carrier’s willingness to shuffle planes around Europe when existing routes offer only marginal returns.

The Chancellor is yet to announce what levies she will raise in the Budget later this month, although she has signalled that “difficult ” decisions lie ahead as she attempts to fill a £22bn “black hole” in the economy.

Mr O’Leary said an increase in APD, which currently stands at £7 for internal flights, would come as a blow after the Irish airline recently poured investment into regional UK airports.

He said: “We’ve put a lot of additional capacity into Glasgow, Edinburgh and Belfast.”

Speaking in Brussels at a gathering of European airline chiefs, he said that increasing APD would put more of a burden on ordinary passengers.

He said: “APD is a penal tax on the poor. The rich don’t care. In a post-Brexit environment, the UK needs to stimulate inward tourism.”

Mr O’Leary said that while the Government was making encouraging noises about aviation and appeared serious about expanding Britain’s airport infrastructure, he would be reserving judgement on the Chancellor until the Budget.

He added: “They’re running around in circles a bit. They’ve overemphasised the black hole in the economy and the need to tax or cut, so let’s see what she does.

“What’s wanted is a competent administration with some pro-growth policies and no more whining about how we don’t want any more air travel and how Boris Johnson is going to lie down in front of the digger if a runway gets built.

“Sir Keir Starmer has said it’s about growth and competitiveness. If he wants to deliver growth the easiest way to deliver it is with aviation and tourism, because we can move planes around and turn that tap on almost straight away.”

Mr O’Leary said he was encouraged by signs that “the green agenda is on the retreat across Europe and people have worked out that what we need now is more productivity”.

He said that Sweden and Ireland had scrapped aviation taxes while Italian regions were removing them on a piecemeal basis: “Some countries will come late to the party but ultimately it’s very positive that you’re seeing governments wanting to stimulate growth rowing back on aviation taxes.”

Mr O’Leary also told The Telegraph that Ryanair was expected to fly 5m fewer passengers than planned next year because of delayed aircraft deliveries from US manufacturing giant Boeing.

The Irish airline expects to attract around 210m passengers in 2025, compared with the 215m previously forecast. That amounts to growth of about 5pc on this year’s expected tally, down from the planned 7pc, Mr O’Leary said.

The Government was contacted for comment.