New trains planned for the East Coast mainline do not work properly with track-side equipment, it has emerged.
East Coast Azuma trains thwarted by northern track
The Azuma trains cause electromagnetic interference to older signals and points in the north of England.
This means the electro-diesel trains can only run on diesel, travelling much more slowly than their promised speed.
Network Rail said it was working with Japanese train manufacturer Hitachi to fix the problem but it was too early to identify a solution.
"We are committed to delivering improved passenger services and are working on a long-term solution," a spokesperson said.
"In the meantime, the new trains continue to be tested on the East Coast Mainline."
The problem affects equipment that registers passing trains and instructs signals and points accordingly.
The older system used on the line north of York does not work with the new trains when they operate on electric power.
Former Labour transport secretary Lord Adonis said he had ordered the new trains 10 years ago.
"They had 10 years to get these signalling issues right," he added.
"They'll be much more expensive to operate, they'll be slower, they'll have less capacity and hundreds of millions of pounds of public money has been wasted again.
"This should be sorted out and it's [transport secretary] Chris Grayling's responsibility."
Mr Grayling admitted there were "teething problems in the same way we had teething problems on the Great Western line".
He said: "We have started to move towards greater integration between track and trains. The new franchises involve much closer working between Network Rail - the track operator - and the train companies.
"The North needs and deserves better railways. It's getting new trains, it's getting investment, it doesn't happen overnight."
Image copyright THE CARLISLE KID/GEOGRAPH Image caption Azuma trains currently cannot travel on electric power past this point near York
The new trains are being assembled at Hitachi's plant in Newton Aycliffe in County Durham.
At expected speed they would reduce the journey time from Edinburgh to London by 22 minutes to four hours, the company said.
Network Rail said they were still due to be rolled out by the end of the year.
Professor Karel Williams, of Manchester University, said the rail infrastructure across the country outside London was underinvested in, but said the East Coast main line had specific problems because it was "electrified on the cheap by British rail in the 1980s".
He said it needed upgrading to the standards of the West Coast Main Line, which was electrified two decades later at the cost of billions of pounds.
The line is now run by by the government as London North Eastern Railway (LNER) after a partnership between Stagecoach and Virgin ran into financial difficulties.
It was the third time in 12 years that a deal to run the route had not been successful.
GNER had a £1.35bn, 10-year franchise taken back by the government in 2006. At the time it was the biggest contract in European railway history.
National Express then agreed a £1.4bn deal in 2007, only to hand it back to the government in 2009 during the financial crisis.