THE row over the proposed rail link to Glasgow Airport has intensified with ministers amid concerns the project is at risk of becoming another Edinburgh trams fiasco. 

On the eve of pivotal talks on the contentious project, the Scottish Government has warned the Labour councils promoting the rail link they will carry the can if it fails to come in on budget and accused them of not producing solid plans..

In a letter to the leaders of Glasgow and Renfrewshire councils, transport minister Humza Yousaf said he was supportive of the link but expressed concerns that a "fully costed business case...has not been forthcoming", adding that the local authorities' plan would be subjected to independent examination before given the go ahead.

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One of the project's key supporters, Glasgow Council leader Frank McAveety, the business case had been made and it was "time for all involved to take the necessary decisions to make the rail link happen”.

The rail link is the flagship project being promoted by west of Scotland councils as part of the £1billion-plus City Deal, with a new business case set to be submitted at the end of this year.

Last week, Renfrewshire leader Cllr Mark Macmillan and Glasgow counterpart Cllr Frank McAveety wrote to Mr Yousaf urging him to express firm support for the project.

But in his response Mr Yousaf said: "As Cllr McAveety has stated in a recent newspaper column, there is over £1bn at your disposal to make this project a success. With this in mind it is surprising that a fully costed business case encompassing the full project has not been forthcoming. I would urge you not to delay in bringing this full business case forward.

"With decision-making comes responsibility and as previously advised by my predecessor, Derek Mackay, the Scottish Government will not fund any financial overruns or increased spend on projects funded through the deal.

"Should projects cost more than initially planned, the Glasgow City Region authorities must be responsible for that additional cost."

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It is understood the national transport agency and others close to the project are concerned that it will become an politicised in the run up to next year's local government elections, with one senior source raising the spectre of the Edinburgh trams fiasco being repeated.

Doubts have also been expressed about the impact of the project on the wider rail network and costs associated with that, such as modifications to Glasgow Central Station.

In his letter, Mr Yousaf said the business plan had to "set out the impacts on all rail users, .... any investment required on the existing rail network, and any compromises on other services", adding these should be "progressed in accordance with industry requirements".

He added: "I understand that these issues have been raised with you by officials from Transport Scotland and Network Rail and am therefore surprised that a fully costed business plan has not been produced."

As well as the three politicians, the meeting will be attended by representatives from Glasgow Airport, Transport Scotland and the chief executives of both councils.

Plans for a link from Glasgow Central to the airport originally secured the support of the Scottish Parliament in 2006.

But with spiralling costs, concern about management of the project and its business case and the fears over the impact of the squeeze on public finances, the SNP scrapped the plan in 2009.

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The Glasgow Airport rail link was resurrected in 2014 after the announcement of the City Deal, an agreement between governments in Westminster and Edinburgh - as well as local authorities - to improve Glasgow infrastructure over the next two decades.

Glasgow City Council Leader Frank McAveety said the current business case already had detailed costs, economic modelling and traffic impact assessments adding it would be delivered on schedule.

Mr McAveety said: “Recent projects which have been supported by Transport Scotland and the Scottish Government include the Borders Rail Link and the Montrose Rail Basin upgrade, both of which had a much less developed business case than that already established by the Airport Access Project.

“The massive potential in the project cannot be realised without the fully engaged support of the Scottish Government and Transport Scotland. The respective leaders of both know that. It is time for all involved to take the necessary decisions to make the rail link happen.”