THE resignation of Nicola Sturgeon as First Minister has come as new calls were being made for an independent public inquiry into the ferry fiasco after the Herald revealed nearly half a billion pounds has been ploughed into the shipyard firm at the centre of the debacle.

Analysis of the money trail based on the Scottish Government's own accounting and audits revealed that the cost to the taxpayer of supporting Ferguson Marine both before and after it forced its nationalisation has soared to more than £450m.

As news of Ms Sturgeon stepping down emerged, Jim Sillars, former deputy leader of the SNP said that she had presided over a "catalogue of failures" including that of the lifeline ferry fleet.

The amount of money pumped into the nationalised ferry delivery firm now exceeds the soaring costs of the Scottish Parliament building.

Early estimates before the referendum of 1997, that the Holyrood building would cost between £10m and £40m would become an embarrassment, as the iconic building ended up costing £414m.

READ MORE: 'Beyond scandalous': Ferry fiasco firm costs taxpayer nearly £500m...so far

Ministers have now overspent against the budget of Ferguson Marine to the tune of over £120m over the last three years alone in the wake of continuing delays in the production of the ferries being built to serve island communities. Their delivery has been put back been over five years in the wake of the soaring costs. It spent double the budget for Ferguson Marine in 2021/22 alone.

The Herald:

The Scottish Government has sanctioned the ploughing in of just over £330m into Ferguson Marine since it was nationalised at the end of 2019 - including a further £60.9m budgeted for the next financial year. - with the firm's key aim to deliver the ferries.

Transport Scotland's business case for the ferries project was just £72m while Audit Scotland's latest update last year expected the final cost of the project to rise to between £238.6m and £243m.

Questions are expected to be raised at the Scottish Parliament next week about the soaring amounts of public money being pumped into Ferguson Marine.

One of the ferries being built by the now publicly owned Ferguson, MV Glen Sannox – which is destined for the Arran-Ardrossan route – was due to enter service in the summer of 2018.

The second vessel, known only as Hull 802, was supposed to be delivered to CalMac in the autumn of 2018 for use on the Uig-Lochmaddy-Tarbert triangle, but that has also been held up.

The delays come against a background of an ferry fleet that is ageing, rusting and failing due to lack of investment.

Some 18 of of CalMac's 35 working ferries deployed across Scotland are now over 25 years old - said by many experts to be the lifespan of such vessels.

The oldest in the CalMac fleet is is the Isle of Cumbrae which is 47-years old.

Since the SNP came to power in 2007, the average age of Scotland's lifeline vessels has soared from 17 years to nearly 26 years. Back in 1974 the typical ferry was just 13 years old.

Six days ago, three of Scottish Government-owned ferry operator CalMac's key vessels remained sidelined with 25-year-old MV Clansman out of action due to rust, delaying her return from a maintenance overhaul.  Yesterday it was confirmed nothing had changed.

Scottish Conservative shadow transport minister Graham Simpson MSP said in the wake of the latest revelations over ferry firm costs that there should be a public inquiry into a "scandal that shamed Nicola Sturgeon and her government".

“Given these latest revelations – and the fact that John Swinney could not guarantee recently that no more public money will have to be pumped into Ferguson Marine – the SNP must throw open the books to Audit Scotland to let them assess what the final bill to the taxpayer is likely to be," he said.

In 2016 Nicola Sturgeon featured in a 'Standing up for Scotland' video at Ferguson Marine. Source: SNP

“The ferries fiasco is not just the biggest scandal of Nicola Sturgeon’s time in office – latest estimates show it’s set to trump the Scottish Parliament building as the most wasteful public spending project in the history of devolution.

“But this abject failure is about so much more than taxpayers’ money being squandered on an industrial scale.

“At the heart of it lie Scotland’s island communities, who have been betrayed by an SNP Government that’s been unable to provide a reliable ferry fleet on which livelihoods depend.

“Nicola Sturgeon’s government is still unable to explain why the irrational and reckless decision to award the fateful contract to Ferguson Marine was made, while the subsequent cover-up has been symptomatic of her administration’s lack of accountability.

“Her successor as First Minister must agree to hold a full, independent public inquiry to get to the bottom of this murky scandal once and for all.”

When the contract was agreed in October, 2015, both ferries were due to cost a total of just £97m - and were to be paid for by CMAL by repaying a ministers' loan over 25 years through using revenue it generates from the fees it gets from the lease of vessels like operator CalMac’s ferry fleet and harbour access fees.

But part of the Scottish Government's special deal to allow then independence-supporting tycoon Jim McColl's Ferguson Marine to win the contract in the wake of concerns by Scottish Government-controlled ferry owners Caledonian Maritime Assets Limited over a lack of financial guarantees, meant that loan was wiped out.

The Herald: First Minister Nicola Sturgeon during a visit to Ferguson Marine Engineering Ltd

The £83.25m that was drawn down to pay for the construction of the vessels was "eliminated" after Ferguson Marine under Jim McColl fell into financial trouble.

It had previously injected £45m in taxpayer-backed loans into Mr McColl's firm which was mostly lost when it fell into administration. It managed to recover just £7.5m from that through the purchase of the Ferguson Marine assets.

The Herald revealed that ministers created a secret path for the nationalisation of the shipyard firm through the provision of the loans.

The Herald revealed that in 2018 when the finance secretary Derek Mackay was telling the public that the loans were being used "to further diversity the business" by moving into innovative areas such as low-carbon marine projects and decommissioning work, internal documents showed the real reason was that Ferguson Marine was in financial trouble and at risk of falling into administration.

An internal memo revealed that one £30m loan due to be paid back in ten years came with it a "right to buy" if the company fell into insolvency.

And it said the loan agreement "specifically creates a path to full nationalisation in the event that that becomes ministers’ preference".

Ministers had by then already given a £15m unsecured loan to the firm in an arrangement that was withheld from the public on “commercial confidentiality” grounds.

A Scottish Government spokesman said: "The Scottish Government’s priorities have always been the completion of the two ferries, securing a future for the yard and its workforce, and supporting our island communities that rely on this type of vessel on a daily basis.

“We deeply regret that the vessels are taking longer and costing more than they should, and we have already committed to a formal review upon completion."