The budget airline blamed Bordeaux Airport for the blunder, branding the incident "unacceptable".

Ryanair said the airport failed to provide the passenger with "the special assistance required" and claimed the crew had been "misinformed" that all passengers had boarded.

In response, the airport refuted Ryanair's account of events and said the passenger and her companion were present in the boarding lounge under the responsibility of the airline, "who decided to depart without taking its own customers into account".

Flight FR 6700 was due to depart from Bordeaux to Edinburgh at 10pm on Tuesday.

The plane had started to taxi on to the runway for take-off when the error was discovered. The pilot then returned to pick up the missing passenger and her companion.

Ryanair said it was working with the airport to ensure "this does not recur".

In a statement, the airline said: "It is unacceptable that Bordeaux Airport failed to provide this passenger with the special assistance required to board this flight from Bordeaux to Edinburgh despite Ryanair paying for this service.

"Not only did they fail to board this passenger, but they misinformed the crew on this flight that all passengers had been boarded when in fact this passenger had not, and the aircraft began to taxi on to the runway.

"Ground staff at Bordeaux Airport realised their error and notified the crew who returned to stand in order to board the passenger.

"It is abysmal that Ryanair customers requiring special assistance are being let down by Bordeaux Airport and we are working with them to ensure that this does not recur."

Bordeaux Airport branded Ryanair's statement "false and defamatory".

The airport said the passenger requested wheelchair assistance from the airline on purchasing her ticket and on arrival was assigned an agent from a company mandated by the airport to facilitate her movements up to boarding.

A spokesperson said: "It should be pointed out that during all this time, the passenger remained under the responsibility of the airline organising her transport. The airport is simply an infrastructure operator.

"When boarding for the flight to Edinburgh began, all passengers were directed towards the aircraft by Ryanair's service provider. The passenger in the wheelchair and her companion were present in the boarding lounge at this time, visible to Ryanair staff and under their responsibility.

"When the support assistant took charge of the passenger and her companion to escort them to their aircraft, they realised that the Ryanair teams had closed the aircraft doors and the aircraft was moving."

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Bordeaux Airport said that's when the pilot was notified and returned.

The spokesperson said: "The airport acknowledges that the agent in charge of escorting the passenger from the boarding gate to the aircraft should have arrived at the gate sooner, and will take all necessary measures to limit customer waiting time.

"However, the two passengers in question were checked on to this flight. They were present in the boarding lounge under the responsibility of Ryanair, who decided to depart without taking its own customers into account.

"It must also be pointed out that the service mentioned by Ryanair is in no case paid for by the airline company, but by all passengers, able-bodied or not, who pay a tax for the provision of said service.

"It is highly regrettable that the airline has taken the liberty of describing a situation without speaking to us beforehand, placing the blame for a fault of its own on the airport."