The policy was introduced in November
Ryanair has been fined €3 million (£2.6m) by the Italian competition authority over its cabin baggage policy introduced late last year.
Since November 2018, Ryanair has charged passengers to bring small suitcases (up to a maximum of 10kg) onto their planes, while small bags are only allowed on for free if they can fit underneath the seat in front of passengers.
Larger bags of up to 10 kilos require a luggage fee, or a fee-paying priority boarding pass. Priority boarding costs customers upwards of £6 per flight.
On Thursday, Italy's Competition Authority (AGCM) issued a penalty of €3 million (£2.6m) to Ryanair, while a penalty of €1 million (£871k) was also imposed on Wizzair.
AGCM said that most passengers expected to travel with a larger carry-on bag and that the airlines were raising ticket prices in a "non transparent" manner by imposing an extra payment on customers.
"Hand baggage is an essential element of the air transport service and its transport must be permitted without incurring any additional costs,"
said AGCM in a statement.
"In fact, also on the basis of the European legislation on air transport, the foreseeable and unavoidable supplements must be included in the price of the basic service presented since the first contact and, therefore, can not be separated from this with the request for further sums.
"Hence the deception for consumers, as the price to be paid at the end of the booking process will almost always be higher than the tariff presented at the beginning of the process."
