Chris Gibb, chief operating officer at Virgin Trains, said the infrastructure company had not paid enough attention to the long-term performance of components used on the West Coast Main Line.
The resulting failures of overhead power lines and other equipment has contributed to Virgin having the worst punctuality performance of any UK train operator, with more than 70% of its delays attributable to Network Rail, he said.
Over the last year, 16% of Virgin Trains' services have been recorded as late, compared to a national average of 9%.
Mr Gibb's comments follow a five-month, part-time secondment with NR, designed to identify actions to improve performance on the southern section of the route.
He welcomed NR's involvement and the willingness of its chief executive, David Higgins, to support his work and accept all 14 recommendations put to the company in a recent report.
But his findings include some harsh criticism of how NR maintains the West Coast Main Line, the busiest mixed-traffic rail route in Europe.
He claimed cost-cutting imposed in the latter stages of the £9 billion upgrade of the route – eventually completed in December 2008 – had led to parts being selected solely on the basis of lowest price and the speed in which they could be delivered.
"It appears the West Coast Route Modernisation team was more focused on within-budget and on-time delivery of the project than the medium to long-term component performance. This has clearly cost NR and the industry dearly in terms of poor performance," Mr Gibb wrote.
He said the approach had built-in, long-term costs as parts would need to be renewed earlier than should be the case. A key shortcoming is that global engineering firms were not prepared to take responsibility for parts failures and ongoing maintenance, Mr Gibb said.
He pointed to Virgin's relationship with Alstom, which built and still maintains its fleet of electric, tilting Pendolino trains. He said: "No-one was prepared to put their name against the upgrade of the West Coast Main Line apart from Network Rail. They are the people to blame. I would have embraced a global supplier so their necks are on the line if anything goes wrong," he said.
He also hit out at Britain's rail regulator, insisting a "punitive" approach to fining NR had damaged staff morale. "The best railway engineers won't come forward to do jobs on the West Coast Main Line because they're right in the Office of Rail Regulation's firing line," he said. Robin Gisby, NR's managing director for network operations, conceded the company still had "a long way to go" in improving long-term reliability of equipment but was moving towards a "whole-life cost" approach when purchasing components.
Mr Gisby said his ability to buy more expensive, but more reliable, equipment depended on agreeing funding with the regulator. Cutbacks imposed on the West Coast Main Line upgrade were partially driven by the ORR's insistence that budgets were reduced, he added.
A spokesman for the ORR said: "Network Rail has been fully funded to deliver a package of outputs, including upgrades to the West Coast Main Line and levels of train service reliability, in a sustainable way, taking a whole-life cost approach to maintaining and renewing the railway."