Network Rail Scotland had the worst delivery rates of planned improvements to railways in the past year compared with other branches across the UK.
The Office of Rail and Road’s (ORR) annual assessment shows that the company fell behind in its work to renew the railway – delivering just 69% of planned work.
It is the lowest delivery of all the company’s locations across the United Kingdom.
The report also found Network Rail Scotland’s wider financial performance was hit by costs of industrial action, payments to operators for poor train performance, and inflationary pressures.
Performance targets for the main passenger operator ScotRail were also missed by Network Rail Scotland, as well as for freight performance – although this showed some improvement towards the end of the year.
However the firm did achieve its target for the Caledonian Sleeper service.
Despite the ORR’s findings, Network Rail Scotland’s reliability was the best of all of the UK’s regions, ending the year above target.
However, under-delivery of renewal work means the regulator will now “scrutinise” Network Rail Scotland’s future renewals plans.
Feras Alshaker, director of planning and performance said: “There is no doubt that the past year has been challenging for the rail industry, passengers and freight services.
“Our assessment is that Network Rail Scotland is delivering a safe network.
“But, working with ScotRail, it needs to deliver its train performance improvement plans and deliver for passengers.
“It must also carefully manage its financial pressures and deliver planned renewal work to make the railway in Scotland as reliable as possible in future years.”
Network Rail has been contacted for comment.