Online train ticket sellers have been warned to be upfront about booking fees, with more than half of those who charge failing to clearly display the eventual cost. The rail regulator has written to seven ticket retailers to highlight concerns about “drip pricing”, in which consumers are shown an initial price before add-ons are revealed later. Some sites and apps were adding fees of up to £6.45 a transaction, a review by the Office of Rail and Road (ORR) found. It said consumers could be “disproportionately influenced” by the initial headline price, and the companies should ensure such fees were included upfront, in line with consumer protection law. As well as booking fees, some sites add finder’s fees for split tickets – where multiple single tickets come in cheaper than the full journey fare, under the UK’s quirky rail fare system. The ORR’s director of strategy, policy and reform, Stephanie Tobyn, said: “Some online retailers are not as transparent as they need to be when it comes to how they display or provide information on additional fees. “We want to ensure consumers are provided with timely and relevant information when making purchase decisions and that drip pricing does not undermine consumer confidence when purchasing rail tickets online.” Train operators are not allowed to charge booking fees on their own websites. The ORR review looked at the websites and apps of 19 third-party train ticket retailers. Twelve were found to charge booking fees: MyTrainTicket, Omio, Rail Europe, Railboard, Raileasy, Sojo, Split My Fare, Train Hugger, Trainline, TrainPal, Trainsplit and TrainTickets.com. Seven of the 12 will receive warning letters from the ORR for not including their fees in the upfront price. The ORR has not yet divulged their names. Alex Robertson, the chief executive at the watchdog Transport Focus, said: “Passengers should not be left in the dark about the cost of their ticket. Online retailers must provide passengers with clear, accurate information upfront so they can make an informed choice.” Drip pricing has become a growing concern for consumers in many sectors, notably the airline industry, leading the government to order a wider review this year. The Department for Business and Trade’s consultation into price transparency and drip pricing closed in October.