Europe's largest airline has adjusted its family seating policy after an investigation was launched into it charging parents to sit with their children on flights.

The budget airline Ryanair said the “minor policy tweak” means “free parent seats” will be available in the rear of its aircraft for future bookings. All children on the booking will be allocated seats alongside them for no fee.

Ryanair has until now required at least one parent to sit with their children aged between two and 11 and also charges for the seat booking.

It does this through what the carrier calls a mandatory family seat, which costs between 4.50 and 13.50 euros each way, the CMA said. Paying to reserve a seat is optional for other passengers.

Earlier this month, a UK government watchdog said it had opened an investigation to determine whether Ryanair’s policy at the time was “in line with consumer law”.

Under the new policy, parents will still have the option of paying to reserve a seat of their choosing, and have their children alongside them free of charge.

Ryanair chief executive Michael O’Leary accused the UK's Competition and Markets Authority (CMA) watchdog of “turning a blind eye” to the “high fares” charged by airlines on routes with no competition from the Dublin-based carrier.

He said: “The CMA has now targeted our family seating policy which has been universally embraced by consumers as the most progressive and transparent in Europe.

“Instead of promoting competitiveness and lower fares for consumers, the CMA is on a mission to force Ryanair to adopt the less transparent and less consumer-friendly family seating policy applied by most other airlines - just because it’s the industry standard.

“We will reluctantly adjust to this industry standard as we don’t want to waste time explaining to misguided regulators how badly they misunderstand what is in the best interest of UK and Europe’s consumers.

“Under our revised family seating policy, families may have to wait until after they have checked in to find out their seat allocation and are more likely to be seated at the rear of the cabin but at least the CMA will be able to claim they have done something for consumers, but sadly most consumers won’t notice.”

Ryanair said the change will be “revenue neutral”.

Rory Boland, editor of UK consumer magazine Which? Travel, said: “It should never have required Which? to report Ryanair’s unfair seating policy to the CMA to prompt action on these unjustified charges.

“It was never fair to charge parents to sit next to children as young as three.

“It’s clear Ryanair is unhappy about being dragged into doing the right thing, so Which? will be monitoring the implications of this policy and whether all parents are seated next to their children without charge over the next few months.” The CMA was approached for a comment.