Network Rail (NR) has apologised to passengers for its "unacceptable performance" on a section of a London to Scotland route.
The problem was on the southern end of the West Coast Main Line, which is operated by Virgin Trains.
NR said that 71% of the delays to Virgin services in the period May 26 to June 22 were attributable to NR, with just over half of these down to problems such as overhead line and track faults.
Just 12.3% of the delays were down to Virgin, which said it would take action for breach of contract.
The problems led to Virgin achieving a trains-on-time figure of only 84.5% in the May 26 to June 22 period, well below the national average.
Overall, train companies ran 93.1% of trains on time during this period, an improvement on the 92.9% last year and the joint best-ever figure for this particular four-week period.
Only two other companies failed to reach at least a 90% figure – East Coast (87.8%) and London Midland (88.5%).
Share