FAILURE of a “safety-critical” component has led to further delays to plans to speed up journeys by electrifying the main Glasgow to Edinburgh rail line.

The revelation by transport minister Humza Yousaf has led to fears the further delay will add millions to the cost of the £742 million upgrade.

It comes after it emerged last year electric cables installed as part of the upgrade were too low and had to be replaced. It was estimated the work on the 42-mile link was at least £32m over budget and seven months late because of the wire issue.

Mr Yousaf admitted in July last year that electric train services between Edinburgh and Glasgow were unlikely to run until next month, seven months behind schedule.

However, Mr Yousaf said the new issues would further delay the start date of “energisation”, the time overhead electric power cables will go live.

The latest problems are expected to further delay the training of ScotRail drivers on the new trains and the running of electric services.

The Herald:

National Rail refused to say what the fault was, but it was understood it is a component of the overhead power lines which may need to be replaced on the whole line.

News of the problems came in a letter to Mr Yousaf from Mark Carne, chief executive of Network Rail Infrastructure, which says: "Regrettably, it is now clear that a safety critical component is susceptible to failure and must be replaced. This will impact the energisation start date.

"We are working extremely closely and collaboratively within the ScotRail Alliance to assess how the impact of this challenge can be minimised for passengers and we will keep your officials informed."

He further agreed to meet with Mr Yousaf to have a "wider conversation" about measures to "improve delivery of projects in Scotland".

Mr Yousaf told MSPs: "I have arranged to speak to Mark Carne to ascertain the full detail of the component failure, which is safety critical. I will, of course, ensure that members are appropriately kept up to date. Any further delay to EGIP [the Edinburgh to Glasgow Improvement Programme] —once again due to Network Rail — would be extremely disappointing."

"This potential further delay again highlights the need for further devolution of governance of Network Rail’s projects, which are ordinarily managed outwith the ScotRail alliance, so that Network Rail is properly accountable to this Parliament and this Government, which of course funds its works in Scotland."

Iain Docherty, professor of public policy and governance at the Adam Smith Business School at University of Glasgow said he was not surprised by the further delays.

The former non-executive director of Transport Scotland said: "Network Rail have been consistently very late and over budget with English electrification schemes. Now it would appear the same thing is true here. It has been delay after delay after delay.

"The disappointing track record in the south has come home to bite here. It will add to the cost which NR will just demand from Scottish Government and the later introductions of the trains, which means people don't get the benefits, the economy doesn't begin to grow and the franchise doens't get the increased revenues. "

More Scottish Government concerns about the EGIP project emerged in a separate letter from Mr Carne to Transport Scotland chief executive Roy Brannen.

Mr Carne said he had been "personally addressing other challenges" where "performance has not been acceptable and action is being taken".

Testing of the new electric Hitachi-built Class 385 fleet of trains began in January, several weeks late, when it was indicated they would be carrying passengers from September.

The four-car train, codenamed T2 by the company, was one of a fleet of 70 trains being built by Hitachi Rail Europe intended for use on ScotRail’s new electrified routes between Glasgow to Edinburgh and other routes in the central belt.

In July, last year, Mr Yousaf said he was "not prepared to accept" delays and increased costs in rail projects run by Network Rail and was concerned about the then seven month delay.

He said Network Rail had informed Transport Scotland the Edinburgh-Glasgow line will not be running electric services until July 2017.

Network Rail would not discuss the extent of the latest delays, instead saying in a prepared statement: “There is an emerging issue around some of the installations on the Edinburgh-Glasgow electrification programme.

"We are working hard to assess the implications of this and won’t be commenting further until we have completed that work.”