THE key document which was believed missing in the ferries debacle which explained why the Scottish Government took the risk with the project has been found.

Transport minister Jenny Gilruth said the key email showed “incontrovertible proof” the decision was taken by former minister Derek Mackay.

It was previously held by the Scottish Government that the key document, which outlined why the decision to award the contract to Ferguson Marine Engineering Ltd (FMEL), did not exist.

Nicola Sturgeon had said earlier in the year it was “regrettable” the reasoning behind the key decision had not been recorded properly.

While the email chain, which Gilruth said had been discovered on the computer files of a civil servant who had left the Government “some years ago”, did not go into the reasons Mackay chose to apparently ignore concerns from experts that the Port Glasgow yard did not offer a full builders’ refund and so made the taxpayer liable for the costs of delays and failure to deliver.

Audit Scotland has said the documents publish today still fail to answer why the decision was signed off. 

But the document shows the decision was ultimately signed off by Mackay during his time as Transport minister.

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It also says that Deputy First Minister John Swinney – who remains in that position – had the final say on the contract being awarded. 

It was announced by Nicola Sturgeon on August 31, 2015 that FMEL were the preferred bidder.

Gilruth announced the find in Holyrood today.

She said: “This email destroys the opposition’s ridiculous conspiracy theories that another minister made this decision and it destroys their unfounded speculation that there was a ministerial direction given.”

Graham Simpson, the shadow transport secretary, said the email failed to show “why the decision was taken”.

He added: “Nor does it say whether there were discussions between Mr Mackay and Mr [Keith] Brown [Mackay’s senior when the contract was awarded] and Mr Swinney and Ms Sturgeon.”

The key document comes as part of a series of new publications from the Scottish Government today on the awarding of two ferries contracts to FMEL, which are now more than four years late and overbudget by double the original price.

Opposition parties have criticised the SNP for awarding the contract to FMEL despite the reservations of civil servants at CMAL who were concerned the state would be forced to bear the brunt of the costs in the event of delays.

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One email in the chain, from a redacted sender to Mackay’s office, said: “CMAL have concluded contract negotiations with FMEL, having secured some improvements in the terms of the refund guarantees to be provided by the shipyard.

“CMAL’s assessment is that this is the best deal that can be negotiated given FMEL’s financing structure. However, it is clear that the Board of CMAL are still concerned at the risks this contract basis presents in placing orders at FMEL without the full refund guarantees in place that were specified in the original tender documents.

“They are concerned in respect of the position this could leave the company if the ship failed to perform or the shipyard went into liquidation.”

The sender, who has been kept anonymous in the publication, asked the transport minister to confirm he had considered CMAL’s concerns.

Mackay’s private secretary replied to the email the following day saying: “The Minister is content with the proposals and would like to be moved on as quickly as possible please.”

Other emails in the chain confirm the contract was discussed with Swinney before it was announced to CMAL the contract was awarded and that “the absence of banana skins” in the procurement process had been confirmed.

Sturgeon had previously told MSPs the Auditor General had said that the “judgement not been withheld, rather an important piece of documentation was not prepared”.

She added: “So there is one link in the chain that is missing, but you can still very clearly follow the chain of events.”

She also pointed out there were around 200 documents outlining the process for awarding the contract to FMEL in the public domain, totalling around 1500 pages of evidence.

A spokesperson for Audit Scotland said: "The email confirms that ministers approved the award of the FMEL [Ferguson Marine Engineering Limited] contract.

"But there remains insufficient documentary evidence to explain why the decision was made to proceed with the contract, given the significant risks and concerns raised by CMAL."