Network Rail faces a fresh probe after missing more than a third of its enhancement works targets last year.
The rail infrastructure operator will be investigated by regulator the Office of Rail and Road (ORR) after failing to hit 30 of 84 enhancement milestones in 2014-15.
Network Rail is in charge of more than £12bn of projects to improve the railway in the five years to 31 March 2019.
The regulator is to investigate whether the company has the right measures in place to plan and deliver the projects it has committed to.
ORR chief executive Richard Price said: “Network Rail has made a slow start in delivering on its enhancements and performance targets for control period 5, and we have asked it to demonstrate how it plans to get back on schedule to deliver on its commitments to 2019.”
Network Rail also delivered less renewal work than it planned last year. Track renewal is 7% behind plan; signalling renewal 63% behind; and overhead line renewal 77% behind.
Overall punctuality of train service performance was at 89.6% – below the organisation’s 92.5% target.
“ORR is investigating Network Rail’s performance improvement plans and delivery of enhancements,” said Price.
“This work will help identify the issues the company needs to address to improve train performance, increase capacity and deliver on its commitments to passengers.”
The Civil Engineering Contractors Association called on the industry to help Network Rail improve.
Chief executive Alasdair Reisner said: “The industry is aware of the challenges that face Network Rail in the delivery of control period 5.
“The scale of investment is unlike almost anything seen before, and comes at a time when the rest of the infrastructure market is also buoyant.
“We need to work with Network Rail to quickly resolve some of these issues, pressing forward with the vital investment in UK rail.”
Network Rail said it recognised the scale of the challenge and had been openly and regularly reporting performance data.
“There are clearly opportunities to improve following decades of under investment in the rail network,” said a spokesman.
“However, it is worth highlighting that we operate the safest passenger network in Europe and the railway asset reliability is the best it has ever been. The increase in passengers means that more people are getting to their destination on time than ever before.
“Network Rail’s new leadership team, under chief executive Mark Carne, is committed to deliver the pace of change required to build a better, more modern network that passengers and businesses can rely on.”
Network Rail escaped without a fine after travel chaos caused by late running maintenance work over Christmas.