Northern's outdated Pacer trains still used in South Yorkshire in 2020
Northern has admitted that some of its heavily-criticised Pacer trains will be used in South Yorkshire next year, despite a pledge to remove them.
The rail firm began rolling out its £500m fleet of new trains in June, saying it would take all Pacers out of use by 2020.
It later said some of the trains - which no longer comply with disability access rules - would be around longer.
A spokesman confirmed "a small number" would be used in South Yorkshire.
Northern, which is owned by Arriva Rail North, has previously said it was "working hard" to scrap all Pacers by the end of this year.
Its franchises cover the North West, Yorkshire, parts of Derbyshire and the North East.
Pacer trains have been regularly deployed on busy commuter routes, including those into Manchester, Leeds, Middlesbrough, Sheffield and York, as well as on the Merseyrail network.
The Department for Transport said in July the Pacers would continue to be used "due to delays in manufacturing new trains".
Meanwhile, the first seven Pacer trains have been retired from daily service. One train - unit 142005 - had travelled more than three million miles since 1987, said Northern.
The trains will be stored so they can be made available in exceptional circumstances.
Pacers were built in the 1980s from the body of a bus frame and intended to have a maximum lifespan of 20 years. They have been dubbed "buses on wheels" and called "museum pieces" by Greater Manchester mayor Andy Burnham.