Andy Burnham has repeated calls for an inquiry into train company Northern after receiving an email from a supposed whistleblower.

The Greater Manchester mayor said the correspondence shows that the under-fire company plans its cancellations in advance, despite representatives repeatedly claiming otherwise.

It comes against a backdrop of poor performance, with beleaguered passengers complaining about high numbers of cancellations often announced at very short notice.

However, Mr Burnham says that an email he received from someone who claims to work for Northern shows that the operator actually plans to cancel specific services the night before the trains are due to run.

The person also claimed that Northern bosses refused to reinstate an agreement with staff around rest day working, a factor that the company put forward as a reason for the recent problems.

Burnham said: "If true, these revelations are very worrying. It now looks like Northern have simply not been straight with the Greater Manchester public

“Unbeknownst to passengers, Northern appears to be planning significant numbers of cancellations for the next day as a matter of course every evening.

“This is in contrast to the company’s public statements claiming that cancellations are often decided at the ‘last minute’.

“The transport secretary must investigate these claims as a matter of the upmost priority.

“Northern passengers need urgent assurances. Just saying everything is fine and improvements are on the way will not cut it.”

The mayor has written to transport secretary Chris Grayling to demand that the government aids in Transport for the North’s investigations into these issues.

Northern regional director Liam Sumpter has said the company only made “last minute changes” to services which led to the delays and cancellations.

He added: “Even station staff don’t always know about these late changes.”

The latest statistics from the Office of Road and Rail, Britain's transport watchdog, show that Northern has had a huge drop in punctuality in recent months.

Only 83% of active services arrived within five minutes of their scheduled time in the last four months to March, down from 91%.