Image copyright Northern Rail Image caption Northern, which is also known as Arriva Rail North, is the main train operator in northern England

Elected mayors have called for the government to take control of rail operator Northern, accusing it of breaking promises to passengers.

Greater Manchester Mayor Andy Burnham and Liverpool Metro Mayor Steve Rotheram accused the firm of failing to deliver promised improvements.

Northern said it was "working hard" to improve the service for passengers.

The Department for Transport (DfT) said it saw no reason to "consider making changes to the franchise".

The latest criticism of the operator's record centred on commuters being crammed on to smaller trains and facing regular delays.

It came a year after widespread rail timetable chaos affected services country-wide.

'Enough is enough'

The mayors said Northern, operated by Arriva Rail North, had failed to tackle issues such as overcrowding and said the number of trains being run with reduced carriages had risen since December last year.

They accused Northern of repeatedly failing to introduce promised commuter services to towns including Knutsford and Northwich, in Cheshire, and said it risked failing to meet its own deadline to phase out ageing Pacer trains by the end of 2019.

Northern ran up to a fifth of its services late and had cancelled 255 services last Sunday, according to figures published by the mayors' offices.

The mayors said they had been forced to intervene to end an industrial dispute with the Rail, Maritime and Transport union (RMT) over the role of guards which halted thousands of Saturday services spanning 47 weeks.

Image copyright Stephen Noble, Tom Bitcliffe, Kieran Trafford Image caption The mayors said the number of trains operated with reduced carriages had risen since December

Mr Burnham said: "We have been extremely patient with Northern but enough is enough.

"They promised us that things would be significantly better by May 2019 and that hasn't happened."

The mayors said the DfT had a "legal duty" to take over as operator of last resort in the same way it had taken control of the East Coast Main Line last year.

Northern's franchises cover the North West, Yorkshire, parts of Derbyshire, and the North East and are due to run until 2025.

Northern managing director David Brown said improvements for customers since last year included "better punctuality", investment in new and refurbished trains and the introduction of more than 2,000 new services.

He added: "These improvements are still a work in progress, but we are making things better for our customers."

RMT general secretary Mick Cash said: "There should now be a swift transition of the Northern routes into a public sector operation. There can be no excuses for any delay."

A DfT spokesman said there had been "much needed improvements" to Northern services since last year.

"At a time when performance is improving and brand-new trains are being rolled out to replace the unpopular and dated Pacers, change could result in significant disruption," he said.