FASTER journey times and longer trains promised under the flagship Edinburgh- Glasgow rail electrification will be delivered as much as a year late, it has been claimed.

Ministers expect the fastest journey time on the route to be cut by 10 minutes, to 42 minutes, by December 2018. Capacity is also supposed to be boosted by the introduction of eight-car trains on the commuter line, which is the busiest in Scotland.

However industry regulator, the Office of Rail and Road, revealed in its annual report on rail in Scotland that both these targets were “at significant risk” as a result of delays to the overhaul of Glasgow Queen Street station, which is due to have its platforms extended to accommodate the new electric trains.

The ORR said Network Rail believed neither the faster journey nor the station upgrade would be achieved by March 2019, and one unnamed industry source told the Sunday Post that December 2019 is “far more likely”.

The source was also reported as saying the continued insistence by Transport Scotland the shorter journey time will be in place by December 2018 was “wholly unrealistic”.

Glasgow and Edinburgh passengers who have faced disruption because of the long-running engineering works have been frequently reassured the works would soon deliver “longer, faster, greener” trains.

Scottish Labour transport spokesman Neil Bibby said: “This is deeply disappointing news for tens of thousands of passengers. Commuters have put up with months of delays and disruption as part of this vital project to electrify the busiest route in Scotland. We are lagging far behind other parts of the UK and the Continent, and missing the 2018 forecast would be a huge setback.”

The £800 million project is already facing a seven-month delay to the completion of the infrastructure works needed to allow electric trains to run between the two cities. This phase has now been pushed back from March 2017 to October 2017. In its annual report, the ORR said this had been “a significant setback on Network Rail’s largest and highest-profile project in Scotland”.

The report continued: “Delivery of a 42-minute journey time and eight-car services between Edinburgh and Glasgow, and the upgrade to Queen Street Station, are now at significant risk ... Network Rail is forecasting the regulated milestone of March 2019 will be missed for both key outputs.”

It blamed the delay on the extra nine months Network Rail now requires to obtain compulsory purchase powers required to buy land around Queen Street Station currently occupied by other businesses. The regulator said this was an an issue “outside Network Rail’s direct control” and it was “satisfied Network Rail did everything reasonably practicable to facilitate the process”.

Despite the warning from the ORR, however, transport bosses are adamant the 42-minute journey time will be delivered by the end of next year.

A spokesman for Transport Scotland said: “The project expect 42-minute journey times to be delivered, as planned, from December 2018. Queen Street redevelopment is making good progress. The current assessment from Network Rail shows construction programme has been rescheduled for completion March 2020, however work is being carried out to mitigate this delay as far as possible.”

Ministers had originally expected the Edinburgh Glasgow Improvement Project (EGIP) to be completed by 2017. The spokesman added the cost of the delay “is being determined by Network Rail and the EGIP Alliance contractors”. He said: “Once this work is complete the minister will provide Parliament with an update regarding both the cost of the delay and the estimated final programme cost.”

A spokesman for the ScotRail Alliance – a partnership between operator ScotRail and Network Rail as the body in charge of rail infrastructure – said it anticipated “incremental” improvements in journey time.

He said: “Our new electric trains will begin operating between Edinburgh and Glasgow by December. Journey time improvements with be incremental, with the Queen Street Station redevelopment to be complete by March 2020.”