Network Rail has been urged to take action to retain train punctuality improvements seen during the coronavirus pandemic.
Regulator the Office of Rail and Road (ORR) said performance has dipped since April but remains better than before the virus crisis.
The proportion of times when a train arrived at a station no more 59 seconds late was 80% in the year to the end of March, compared with 65% during the previous 12 months.
During the period from April to September, the figure dropped to 77%.
Network Rail’s Wales and West region – which covers Wales, south-west England, west England, the Thames Valley area and London Paddington station – has had the largest decline, partly due to problems with tracks.
The ORR has called on Network Rail to update its performance plans and targets, address issues in the Wales and West region, and work with the rail industry to develop a strategy for using a £40 million innovation fund.
ORR chief executive John Larkinson said: “The pandemic continues to have an impact on all aspects of running the railway, including staff availability and passenger usage.
“And, in that context, Network Rail and the wider industry are continuing to deliver their essential services well.
“As passenger numbers and freight continue to grow, a reliable and punctual train service performance will be a priority for all users.
“So, it is important that Network Rail delivers on its own commitments to maintain the network in good condition and also provides clear information on timetable choices.
“Network Rail must work with the wider industry to address performance and capacity challenges and do so transparently.”
A Network Rail spokesman said: “We welcome the ORR’s recognition of improvements in train performance compared with before the pandemic.
“Working closely with partners across the industry, we are already addressing the issues raised so that we can continue to provide punctual services for passengers and freight as demand picks up.”
The ORR also announced that it has closed its 18-month investigation into Network Rail’s impact on poor performance in its North West and Central region.
The inquiry found that Network Rail has shown a “genuine commitment” to improving punctuality in the area and has addressed 25 recommendations made by the regulator.