The budget carrier said under EU law, passengers must complete the check-in process directly with their airline to ensure they are informed of safety and regulatory protocols.
It said the issue had come to its attention last week when a small number of passengers who booked their Ryanair flights through Kiwi.com arrived at the departure gate without "official" Ryanair issued boarding passes.
Director of marketing Dara Brady accused Kiwi.com of circumventing "essential aviation regulations" by issuing their own boarding passes and confirmed any passenger presenting a Kiwi.com boarding pass would be refused boarding.
Kiwi.com, though, has refuted Ryanair’s claims. "Threatening not to board customers is petty and an evil Ryanair practice to try and stifle customer choice," said a spokesperson for the firm.
"There is no such ‘fake’ boarding pass – Kiwi.com complies with all the requirements to ensure safe travel for our customers and have done so for years. As well as providing customers with the Ryanair boarding pass, we have also placed it on a Kiwi.com branded background – all the information is the same, just the colours are different."
‘Nothing short of cruel’
The spokesperson further suggested Ryanair was attempting to penalise the firm by selling Ryanair fares cheaper than offered by the airline itself. "The real reason for this action is because Kiwi.com often sells Ryanair tickets cheaper than Ryanair and they don’t like it," they said.
"Ryanair’s behaviour is nothing short of cruel by putting profit ahead of consumer choice. We will do everything in our power to support our customers through this despicable behaviour from Ryanair who are punishing travellers just because they don’t like competition."
It is the latest in Ryanair’s long-running spat with the OTA sector and the so-called practice of "screen scraping" where third parties sell tickets at a profit; this, though, has come under greater scrutiny during the pandemic owing to the refund crisis in travel.
Airlines have been required to issue vast numbers of refunds due to Covid, with Ryanair’s alone totalling more than €1.5 billion (£1.3 billion) to date. Ryanair claims its efforts to refund passengers have been hampered by third party bookings. It is urging people to book direct and "avoid booking via third party agents".
