A branded pre-paid card for Ryanair passengers launched on Tuesday has been criticised by consumer group Which?
The airline's passengers must sign up for the Ryanair Cash Passport to avoid an administration fee of £6 per person per journey.
However, as with many pre-paid cards, charges are levied for withdrawing cash or not using the card for six months.
Which? described the card as an "insult" to customers, but Ryanair said the card would be more accessible.
The specific type of card that avoided the Ryanair administration fee had previously been changed from the Electron card to Mastercard pre-paid cards. Anyone using the Mastercard pre-paid card will be charged from November.
When the new card was announced, a Ryanair spokesman said that 25% of all UK bookings were made using a Mastercard pre-paid card.
He said that the airline hoped to increase this proportion by changing to the new Cash Passport card that, unlike the current cards, would be available on its website.
But Which? said that switching to the new card complicated the process further and added "insult to UK consumers who have little opportunity to avoid such fees".
The card will need to be pre-loaded with cash before any booking is made. There will also potentially be additional costs to anyone who signs up for the new card.
It will initially cost £6 to buy, although each customer will be given a £6 Ryanair travel voucher. Charges include a fee for withdrawing cash from the card over the counter at a bank or from an ATM.
There is also a 50p charge for all transactions, other than Ryanair bookings, from April 2012 and a rolling fee of £2.50 if a card is not used for six months.
The OFT recently held an inquiry into card surcharges for passengers booking travel online. Ryanair said that its charge was for administration purposes, such as the cost of running a website, rather than a surcharge for using a credit or debit card.