Ryanair requires at least one adult to sit with children aged two to 11. The airline's website states that children are given reserved seats free of charge, but a parent or guardian must pay to book a seat next to them, the CMA says.
Ryanair is the only major airline serving the UK that charges this type of fee, the authority claims.
"Our policy complies with all relevant laws and regulations. Ryanair looks forward to refuting these false claims," the airline said in a statement, according to Bloomberg.
The fee is usually 8 pounds (equivalent to about 100 kronor), according to the CMA.
