Passengers in Wakefield could face higher fares because the same company runs both rail and bus services.
The Competition and Markets Authority (CMA) has expressed concern about the overlap between rail and bus routes operated by Arriva.
It has identified train services between Leeds and Sheffield and between Wakefield and Sheffield as well as two bus routes in the Huddersfield area where passengers could suffer higher fares because of the lack of competition.
Restrictions on fare rises could now be imposed on those routes to protect passengers.
Arriva became the main operator of local train services in Yorkshire in April after it was awarded the northern rail franchise for the next nine years by the Government.
Phil Evans, who chaired the CMA’s inquiry, said: “We have not identified competition concerns arising from this merger on most routes. We recognise Arriva’s commitment to bringing a range of benefits through the Northern rail franchise to passengers, such as better trains and improved customer service.
“Our remedies will protect passengers in the relatively few local areas where we have identified competition concerns. We are now inviting responses to our provisional findings and remedies notice, and will continue to assess all the evidence before we make our final decision.”
Chris Burchell, Managing Director of Arriva UK Trains, said Arriva was “committed to continuing to engage constructively with the CMA to resolve their concerns and demonstrate that the award of the Northern rail franchise doesn’t lessen competition”.