The airline’s boss said it was forced to increase capacity on the Belfast-London route due to a passenger cap at Dublin Airport.

Ryanair currently offers flights to and from Belfast International Airport and London Stansted.

In recent months, the company has been in dispute with Dublin Airport and the Irish Department of Transport over restrictions on flight and passenger numbers.

Ryanair CEO Michael O’Leary recently claimed that a one-way flight from London to Dublin could cost €500 (£424) this Christmas.

The low-cost airline said on Monday that it wanted to offer 270,000 additional seats to and from Dublin and London for Christmas, but that this had been prevented.

Passengers were urged to “book their Christmas flights to/from Dublin early this year as airfares (especially from London) are rising rapidly.”

According to the airline, Irish passengers travelling home for Christmas will have to fly via Belfast due to restrictions on Dublin passengers.

Mr O’Leary also criticised Irish Transport Minister Eamon Ryan.

Mr O’Leary said: “We recommend that passengers travelling to Dublin this Christmas book their flights early as cheap seats sell out quickly.

“Currently, at the end of August, our cheapest fares from London to Dublin on Friday 20th, Saturday 21st or Sunday 22nd December are fast approaching the €100 mark one way as the Government has not allowed airlines to operate additional flights to/from Dublin over Christmas.

“Once again, Ireland’s Green Transport Minister has done nothing. Not only is Dublin the second busiest city in the world, but Dublin Airport is the only capital city in Europe to have opened a second runway, which we are not allowed to use due to a 17-year-old traffic restriction.

“We expect airfares to Dublin to reach €500 one way this year as the Christmas period approaches and seats are filled. We therefore urge passengers wishing to travel home to their families for Christmas to book their journey early and avoid the record high airfares that will result from Eamon Ryan’s refusal to remove a 17-year-old, outdated and irrelevant traffic restriction.”

The Irish Department of Transport was asked for comment.

Watch: Belfast teenager makes passengers pause at Dublin Airport with moving piano performance