Business leaders have slammed disruption to train services, describing the region's rail infrastructure as 'not fit for purpose'.

The chairman of business body the New Anglia LEP, Doug Field, has written to both the managing director of Greater Anglia, James Burles, and the transport secretary to express his "dismay" over disruptions to both rural and the Norwich to London in 90 minutes services.

MORE: Train services hit by further cancellations and delaysGreater Anglia's rural services have been plagued with signalling errors and train faults this month.

Problems with its new fleet of Stadler trains have also emerged, which have been introduced on the rural routes, but Greater Anglia has said that is not the "root cause" of the chaos.

Greater Anglia confirmed yesterday that services between Sheringham and Norwich as well as the Ipswich-Peterborough line would not return to normal until next year.

In his letter to transport secretary Grant Shapps, Mr Field wrote: "Given the geography of Norfolk and Suffolk these [rural] routes are critical."

However, he added that new trains could not be blamed for disruption on the London to Norwich routes, where they are yet to be introduced.

Mr Field expressed his disappointment that the "big prize" of Norwich in 90 - which the LEP and the businesses it represents has campaigned for years for - is also being impacted.

"There have been a higher number than usual of cancelled trains on the London to Norwich route, which is yet to have the new trains," he wrote to Mr Shapps.

"We would ask you to ask your officials to investigate as a matter of urgency what has gone wrong and what is being done to remedy the situation."

Analysis by this newspaper showed that between November 11 and 22, the 9am, 90-minute service ran on time just twice from Monday to Friday.

It was delayed by nearly 30 minutes on two occasions.

A week later every 11am and 5pm service between Monday and Friday were delayed by between two and 39 minutes.

Mr Field has also urged caution on the introduction of the new trains on the London line until the Department for Transport can be assured there will be no repeat of the same delays which have hit the rural routes.

He also pushed for compensation for passengers.

In his letter to Mr Burles he wrote: "Whilst we appreciate that you will be working flat out to remedy these issues, it would be very helpful to have a comprehensive briefing on exactly what went wrong, and understanding of why this was not anticipated and what you are doing about it."