The opening of a new £7billion railway line has been delayed after a row between trade unions over who should operate the trains' doors.
East West Rail (EWR) is one of the Government's leading rail schemes, reopening a disused rail route since the 1960s and will eventually link Oxford and Cambridge.
It has been unavailable for public use despite the Government saying it would open this year and empty passenger trains running up and down the new lines for several months.
The Telegraph reported that an insider said some of the delays were due to "our trade union colleagues ... holding us up on opening the doors".
The dispute between the unions and the train company is believed to be focused on who should open the train doors - the guard or the driver.
Unions are against drivers operating the doors because it would delete the guard's job, reducing union membership and income in the long-term, but also meaning the driver could be accountable for any so-called "trap and drag" accidents with passengers.
Shadow Transport Minister Jerome Mayhew accused Labour on Tuesday of emboldening the unions by previously conceding to pay demands.
"Only in Labour's Britain could a £7billion railway be held up because the unions can't agree over who presses the door button," he said.
The rail route will eventually link Cambridge and Oxford
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"Passengers have waited years for this line, and now they're being left standing on the platform because Labour don't have the backbone to stand up to their union paymasters," he said.
"Since day one, Rachel Reeves has blown billions showering her union paymasters with inflation-busting deals - 15 per cent for train drivers - and they've smelt weakness ever since."
Mr Mayhew added that it was "militant unions making the demands, and weak Labour ministers waving them through".
"The Conservatives will not stand by while Britain is held hostage by strike barons and a Government too weak to fight back," he said.
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Shadow Transport Minister Jerome Mayhew criticised Labour
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EWR's operator Chiltern Railways, which was appointed in March, wants drivers to operate the doors as it is currently done on most of its commuter services.
Driver training on empty trains are done on Class 165 diesel units introduced by British Rail in the early 1990s - they were designed for driver-only operation.
The class 166s are used by Chiltern Railway on serves out of London Marylebone along with the Paddington-to-Cornwall operator, Great Western Railway.
Both the Aslef and RMT trade unions are against the driver-only operation.
Both the two unions - representing drivers and guards respectively - can extend the delay of EWR's opening unless their demands are met, senior insiders have told the Telegraph.
It is reminiscent of South Western Railway's attempts to introduce a £1billion fleet of new trains in recent years.
The efforts were delayed by an identical row over jobs and control of train doors.
Delays to EWR also included Chiltern Railways declaring a brand-new station on the line was unfit for purpose.
“On Chiltern and EWR, we can confirm that management have written to the union spelling out their plans for driver only operation. We are seeking talks and RMT’s standing policy is that we are opposed to this," an RMT spokesman said.
An Aslef spokesman said the train drivers’ union was initially told by Chiltern about its door plans in October, adding that shop stewards have declined to start negotiating with bosses until the RMT has had its say.
"We are supporting Chiltern Railways as they work closely with unions and other industry partners to get services on the first phase of East West Rail up and running as soon as possible," a Transport Department spokesman said.
"The East West Rail project is transformational, unlocking thousands of jobs and homes, kickstarting hundreds of thousands of pounds of economic growth for communities across England. It is crucial that services on the completed phase of this programme are allowed to start, and the benefits of this scheme can begin."