Southern and Thameslink passengers have experienced some of the ‘worst performance on the rail network’ since services began, according to a new report.

Government spending watchdog, the National Audit Office (NAO), said Thameslink, Southern, and Great Northern (TSGN) franchise travellers are not getting value for money and have suffered the worst disruption since starting in September 2014.

Research found industrial action to be a ‘major contributor’ to cancellations and delays but also decisions made by the Department for Transport (DfT) ‘negatively impacted on passengers’.

NAO head Amyas Morse said: “Over the last three years long-suffering passengers on the Thameslink franchise have experienced the worst performance on the rail network.

"Some of the problems could have been avoided if the DfT had taken more care to consider passengers in its design of the franchise."

The NAO’s inquiry added that the ‘complex and ambitious’ franchise has the highest number of passengers in England and includes four major train services which operate on a congested railway network with ‘unreliable’ infrastructure.

It said DfT officials failed to grasp the potential impact on passengers of combining an increase in capacity, targets to improve services and expansion of driver only operated trains, which has led to strikes by trade union members.

A large amount of the disruption is caused by train crew shortages.

The DfT and Govia say industrial action was the biggest cause of this, although the operator has also been hit by a shortage of employed drivers.

Between the start of the franchise and August 2017 the DfT made franchise payments of £2.8 billion to Govia and received £3.6 billion from train tickets.

Shadow transport secretary Andy McDonald said: "The National Audit Office's claim that passenger misery could have been avoided if the DfT had taken more care to consider passengers is true for the entire railway."

A DfT spokesman said: "The NAO report confirms that the primary cause of delays and cancellations to passengers has been lack of available staff, which is a direct result of strike action.

"It is time for the RMT to call off its needless strike action."

He added that the level of disruption during the franchise has been "unacceptable" but the department expects the improvement in reliability over the past 12 months to continue as the Thameslink programme is completed this year.