CalMac's spend on unplanned maintenance of the ageing ferry fleet has more than trebled in five-and-a-half years, it can be revealed.

Details from the state-owned ferry operator shows that over the period some £16m has had to be spent on the unexpected repairs.

While an average of £147,377-a-month was being spent on the CalMac fleet nearly six years ago the bill has risen to £481,310 now.

Concerns have been raised that some £3,850,483 was spent on unplanned ferry maintenance in the first eight months of 2023/24 - already the highest since CalMac began tracking the spend.

It represents a rise of more than £800,000 on the bill for the whole of 2022/23.

The Scottish Conservatives, who have been tracking in the costs, said it was the "inevitable consequence of the SNP government’s rampant neglect of islanders, and the lifeline ferries on which they rely".

It comes after the Herald revealed that one of the biggest and oldest vessels in Scotland's lifeline ferry network is set to be sidelined for nearly three months.

READ MORE: State shipyard firm says abandoning 'green' fuel will stop Scots ferry fiasco delay

The 30-year-old MV Caledonian Isles which serves on the Arran route, one of the busiest on the Scottish coast, and is due to be replaced, has been out of action since going for an overhaul at the start of January.

It was sidelined for over three months with further steelwork and engine difficulties this time last year. Further steelwork problems were attributed to a further period spent in the yard in early 2022.

The vessel has been found to have had major technical problems and is now not expected back till at least the end of next month.

Users have been told that the vessel needs "extensive steelwork" leading to concerns that it is suffering rust issues.

MV Caledonian Isles arrived at the Cammell Laird yard facility in Liverpool on Sunday for repairs and there is a race against time to get it available in time for the summer timetable to kick in on March 29. CalMac has said it is expected to be sidelined for four to six weeks.

The Herald:

Meanwhile, new ferries Glen Sannox and sister ship Glen Rosa, which were due online in the first half of 2018, with both now due to serve Arran, are at least six years late, with costs expected to be quadruple the original £97m contract.

Glen Rosa was meant to be delivered to CalMac in August 2018, but that is currently scheduled for May 2025.

Glen Sannox, was launched by Nicola Sturgeon nearly seven years ago and the last analysis estimates that it was not not expected to be handed over till July at the earliest.

But the dates of arrival have been constantly in a state of flux as their construction has been plagued by design challenges, cost overruns and delays.

Since the SNP came to power in 2007, the average of Scotland's lifeline vessels has soared from 17 years to over 25 years. Back in 1974 the typical ferry was just 13 years old.

Three years ago, on May 16, 2021, we revealed that more than half of Scotland's lifeline ferry network was operating outwith its working life expectancy of 25 years.

Since 2010 only five vessels have been launched to support the CalMac network, and only two are considered as major ferries. They are the 5626 tonne MV Finlaggan, built in Poland in 2011 and the 9058 tonne MV Loch Seaforth built in Germany and launched in 2014.

The Herald:

Before 2010, vessels were being produced at a rate of one every 14 months. Afterwards ferries were typically being produced every 33.6 months.

A ferry user group official said that the extent of the "patching up" work that has had to be done to the ageing fleet was "nothing short of scandalous".

"This just shows the level of oversight that there has been in delivering lifeline ferry services in Scotland," he said. "This level of neglect would not have been tolerated if it involved services in the central belt."

Scottish Conservative shadow transport minister Graham Simpson MSP said the neglect was a “colossal scandal” according to shadow transport spokesman Graham Simpson.

As cancellations and costs have spiralled, he said that islanders face “needless misery” from “unreliable and frequently disrupted services”, while mismanagement of ferries has cost the Scottish taxpayer hundreds of millions of pounds.

“Much of CalMac’s fleet is at or beyond the end of its natural life, and is therefore prone to break down," said Mr Simpson.

“This unplanned maintenance is not only taking money away from CalMac’s other priorities and imposing costs on the Scottish taxpayer – it means that islanders have to suffer unreliable and frequently disrupted services.

“The SNP-Green government’s mismanagement of ferries – in procurement, replacement, funding and maintenance – is a colossal scandal.

“It has cost hundreds of millions of pounds, inflicted huge damage on island economies, crippled tourism, and caused needless misery for some of our most vulnerable and neglected communities.”

 A Transport Scotland spokesman said: “Maintenance spend is a requirement of all ferry fleets spend and CalMac are investing additional sums to improve fleet sustainability and to provide a more resilient service for customers and communities, ensuring all planned and unplanned maintenance can be met.

“Our Islands Connectivity Plan has been published for consultation, looking at a wide range of issues, from improving fleet reliability and monitoring performance, to reducing carbon emissions and making future contracts more flexible to respond to community needs.

“We recognise the impact that delays and disruption have regrettably had on our island communities and are committed to investing in our ferry services. Delivering six new major vessels to serve Scotland’s ferry network by 2026 is a priority for this government. We have invested more than £2 billion in our ferry services since 2007 and we have outlined plans to invest around £700 million in a five year plan to improve ferry infrastructure.

“We share the desires of island communities for sustainable and effective ferry services and look forward to continuing our constructive engagement with them on future services and vessel replacements.”

Robbie Drummond, chief executive of CalMac, said: “With one third of our 35 vessels operating beyond their life expectancy, we are investing heavily in both planned and unplanned maintenance as we work hard to provide the best possible service we can to the communities and customers we serve. This investment in maintenance grew to well over £43m in 2023, compared with just £20m in 2017.

“We are looking forward to welcoming a total of six major and 10 small vessels into the fleet over the next five years. However, we face a difficult period as we wait in anticipation for them to be fully operational on the network.  In the meantime, we will continue to work in partnership with local stakeholders and communities to ensure the best possible outcomes for all who rely on our services.”