The ORR says hold-ups caused by Network Rail are up to 25pc more than projected

The Office of Rail Regulation hauled Network Rail's chief executive, Iain Coucher, into a meeting last month to explain why delays attributable to the infrastructure operator were running ahead of a joint plan it had put together with the train operator.

Frequent delays on First Great Western services from London Paddington - exacerbated by the botched introduction of a new timetable - have caused howls of protest from passengers.

Last month, in its quarterly monitor of Network Rail's performance to June 23, the ORR said the First Great Western train service "continues to suffer from very high levels of delays attributed to Network Rail". Pointing to a series of "major incidents", the ORR said hold-ups caused by Network Rail were 15pc-25pc more than projected in the "joint performance improvement plan" - a situation since aggravated by July's floods.

Describing Network Rail's performance as "exceptionally disappointing", ORR said it had recently met with Mr Coucher "to seek assurance that everything possible is being done to turn the situation round quickly ".

In a letter last week to Alison Forster, First Great Western's managing director, the ORR said it had made clear that unless Network Rail cut delays "or convinced us that it was taking every possible step that it reasonably could to do so, we would have to consider the possibility of enforcement action".

The letter went on to say, however, that "in the light of what we heard at that meeting, and of further written responses from Network Rail, we have decided to hold back from that course for the time being".

Industry sources said the ORR's apparent backtracking reinforced views expressed by Gywneth Dunwoody MP, chairman of the Commons Transport Select Committee, that "when it comes to enforcing the licensing conditions of Network Rail, the ORR has got significant powers, but it appears meek and reluctant to use them".

Chris Bolt, the ORR chairman, denied that the First Great Western situation supported such a view. "Absolutely not," he said. "It is entirely consistent with our approach which goes through an escalation process. This is the last step before there is enforcement."

He pointed out that the ORR had only last week fined Network Rail £2.4m for weak planning and execution of the Portsmouth resignalling scheme.

Sources close to First Great Western said the ORR had effectively put Network Rail on probation.

FGW goes back to the future

First Great Western, the embattled train group owned by First Group, is to ditch its modern trains and replace them with 30-year-old Intercity 125s.

The move will see the company phase out 14 Adelante sets which have 280 seats each in favour of 10 older, yet refurbished, pieces of rolling stock that each seat 515 passengers.

The company said it was making the switch to increase capacity as well as reliability. It runs services from London to cities such as Cardiff and Bristol.