NICOLA Sturgeon has insisted it was Derek Mackay, not the Deputy First Minister, who signed off the award of botched ferries contracts to Ferguson Marine.

The First Minister was pressed repeatedly by Douglas Ross about redacted emails released on Wednesday which she said put it “beyond any doubt” it was shamed former transport minister Mackay who gave the go-ahead for the deal.

But the emails, sent on October 8, 2015, appeared to show John Swinney had given the final “green light”, said the Scottish Tory leader.

Ross said the email chain, hailed on Wednesday as the “key” missing document by the current transport minister, also showed the Government had accepted the deal was open to legal challenge - but Sturgeon pointed out this had not come to pass.

READ MORE: Key document in CalMac ferry saga is FOUND, SNP transport minister announces

The emails between Scottish Government civil servants contain the message: “The Minister [Mackay] is content with the proposals and would like to be moved on as quickly as possible please.”

Sturgeon said this confirmed her previous statements Mackay had signed off on the proposals in his former role as transport minister.

She said because Swinney had not been copied into advice about the measures in place to "mitigate" the risk of the yard's lack of a full builder's refund guarantee, he could not have had the final say on the decision. 

Sturgeon added: "The reasons for the decision are clear. The basis for the decision, in particular, the mitigations that had been put in place to address the risk of no full refund guarantee, are set out in the paperwork.

“It is clear that the decision that was taken was taken on the basis of all of the mitigations set out in the paperwork of October 8, 2015.

“That was paperwork that wasn’t copied to John Swinney that went to Derek Mackay as Transport minister and Derek Mackay took the decision.”

But later exchanges between the civil servants show one wanted to speak with Swinney about the proposals before the Government informed Caledonia Maritime Assets Ltd (CMAL), the state-owned firm responsible for ferry infrastructure, that the contract had been awarded to Ferguson Marine Engineering Ltd, at the time owned by tycoon Jim McColl.

READ MORE: Key ferries contract document 'not withheld, it was not prepared' says FM

A later email confirmed one civil servant had spoken with Swinney and then told colleagues: “He now understands the background and that Mr McKay has cleared the proposal. So the way is clear to award.”

Ross said this proved the Deputy First Minister had the final say on the award of the contract.

He added: "His hands are all over this dodgy deal.

"The stench of cover up and corruption is running through this whole sorry affair."

Speaking after the exchange, Swinney told reporters in Holyrood he had given "budget approval" but not the final say on the deal. 

He said: "As finance secretary at the time, I’m responsible for providing the budget for the meeting of any contracts.

“What officials were doing was briefing me that there was no need to change the budget arrangements based on the contract that had been agreed and approved by the transport portfolio, and which of course is confirmed by the email trail you got yesterday.

"What I gave was the budget approval, which I had given in August.

“And the budget approval I gave in August of 2015, the officials assured me on October 9 did not need to be changed.

"I didn’t give it the final nod."

Ross demanded Swinney come before parliament immediately to answer questions around why he had allegedly given the final go-ahead, according to Ross, despite concerns raised by experts at CMAL who were concerned about the lack of a refund guarantee in case the yard closed or the project was delayed. 

In the absence of this guarantee, the state has footed the bill for the problems with the project. 

The two ferries are being built at the now-nationalised Port Glasgow shipyard and are more than four years late and more than twice their original budget, costing the government around £250 million.

Opposition MSPs have attacked the SNP for signing off on the deal despite it not containing a clause which would have protected the state from the costs of delay to the project. 

Audit Scotland said the missing documents revealed on Wednesday still failed to answer why the contract was awarded without the refund guarantee. 

Prior to the discovery of the document revealed by Jenny Gilruth in parliament yesterday, Sturgeon had insisted the document detailed the reasons the project was signed off had not been prepared, in response to "ridiculous" opposition claims it had been covered up to avoid scrutiny.