DELAYS in modernising the Great Western Railway in the south west could mean extra services on the Mid Cheshire will be postponed until 2018.

When the Arriva-backed franchise won the bid to run the Northern network in December 2015, part of the agreement included extra services on the Mid Cheshire line from December 2017, with two trains an hour between Manchester and Chester.

One of those trains will be an 'express' service, stopping at the main town's on the line, including Knutsford and Northwich.

But those extra services in the franchise announcement relied on rolling stock being 'cascaded' from the south west, where the trains currently operate in the West Devon and Cornwall area as part of the Great Western Railway.

However, a delay to the programme of works on the Great Western Railway, means diesel trains operating in the area need to be retained for longer than first thought as new electric trains could not be ordered until the electrification work has taken place.

Northern said it was 'early days' in terms of the update in the 'cascading' programme but the Guardian understands that it is not certain the delay in the rolling stock will mean the Mid Cheshire line improvements are affected.

A report released this week by the National Audit Office highlighted the delay to the Great Western programme and added that trains would have to stay in the south for nine months longer than agreed.

"The Department expected that west Devon and Cornwall routes would then release Class 153 and 150 diesel trains to support service improvements on Northern franchise routes allowing further onward cascades," the report states.

"In the wider rail network, passengers on Northern franchise routes may have to wait an additional nine months as trains are retained in the west to protect services."

Plans for a phased programme of benefits to be delivered to customers as part of northern programmes - the largest railway upgrade in the north of England since Victorian times, were unveiled this week in a separate announcement.

Alex Hynes, managing director for Northern, said: “This programme will deliver transformational improvements to the services we offer our customers.

"The phased approach will enable us to launch new services, such as new direct routes into Manchester, as infrastructure upgrades are delivered.”