Transport Minister Humza Yousaf has been accused of "passing the buck" after admitting he does not know how much another delay to a flagship rail improvement project will cost.

Mr Yousaf told MSPs there had been a "further delay" to the Edinburgh Glasgow Improvement Programme (EGIP), which will see the busy line between Glasgow Queen Street and Edinburgh Waverley stations electrified.

The work is being carried out by Network Rail, and the minister said he would have to defer to it as to what the financial impact of the delay will be.

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The project, which was originally costed at £742 million, was due to be completed by the end of 2016, although that was later pushed back until July 2017.

Mr Yousaf has now said it will be October before all the work is complete - a delay he said is "extremely disappointing".

He was pressed on the issue by Tory West of Scotland MSP Jamie Greene, who said: "The Edinburgh Glasgow Improvement Programme was supposed to cost the taxpayer £742 million. However just under a year ago it was reported that this had already risen by £32 million.

"Can the minister outline today if he expects any further increases to the cost of the improvement programme and can he tell Parliament if these additional costs will impact any other rail projects or rail funding in general?"

Mr Yousaf said: "I would have to defer to Network Rail to come back to us with what the potential costs increases would be."

Mr Greene responded: "The minister is somewhat passing the buck to Network Rail.

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"Surely as the minister in charge of transport in Scotland he would have some oversight, and indeed be able to share with this Parliament, as to the costs of this project.

"We now know electric trains won't actually be delivered on the Edinburgh-Glasgow line until October this year, that's nearly a year after the original 2016 deadline."

Mr Yousaf said: "I'm sure he doesn't expect me as the minister for transport to be literally on the wires, on the lines, delivering this project. It is delivered by Network Rail.

"Yes we have responsibility as the funder, but we are the client, the delivery of the project is done by Network Rail."

He said there is a "funding ceiling" for the flagship rail project, and he does not expect costs to go above this.

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The minister also made clear: "It is unacceptable that we fund these projects yet the accountability remains with Network Rail."

He said he is keen to sit down with the new railways minister in the UK Government "as soon as possible", as he argued: "It is not an acceptable position that we fund these major projects, we are the client of these major projects, yet the delivery by Network Rail is not accountable to this Government or this Parliament."