SIX vital ferry replacements for lifeline Scottish services due to be in service by last year have failed to materialise - as it emerged almost half the fleet should be retired.

As the full extent of the crisis on ferry links to the Highlands and islands has emerged, the Herald can reveal that according to an eight-year-old plan by Scottish Government's transport agency, six replacements for deteriorating car and passenger ferries which are up to 19 years past their working life were supposed to be delivered by last year - and none of them have been built.

It comes as islanders from Arran to Islay have lodged complaints to ministers about disruption and cancellations to services as the ageing Scottish ferry fleet falters.

While industry experts agree the working life of the ferries is 25 years, the Herald understands 14 of the 33-strong ferry fleet run by taxpayer-owned operator CalMac is older than that, with eight past their 30th birthday.

A replacement for one of the oldest in the fleet, the 37-year-old MV Hebridean Isles,is not expected to be built till at least the middle of 2023 - over seven years late. Plans to replace the ageing ferry serving Islay have not yet even gone out to tender - four years after Transport Scotland said it would actually have been built.

READ MORE: Scottish ferries fiasco - Questions over shipyard deals as illegal 'state aid' cases emerge

According to a 2012 Transport Scotland plan six ferries were due to be completed by 2019, with two, including the Hebridean Isles due online by 2016.

The other due by 2016 was to replace the oldest vessel in the fleet, the 44-year-old Troon-built MV Isle of Cumbrae which originally served the Largs to Cumbrae crossing before serving the Isle of Mull and the Kyles of Bute before serving the Tarbert to Portavadie trip. Between 2016 and 2018 seven faults were reported on the vessel and a gear box had to be replaced.

One of the four due to be replaced by 2019 is the 33-year-old MV Isle of Mull which serves Craignure on Mull from Oban. Another is 34-year-old MV Loch Riddon which is the second vessel serving the Largs to Cumbrae crossing.

The plan also involved replacing 34-year-old MV Loch Linnhe, which began on the Largs to Cumbrae crossing and is now a relief vessel.

Those are on top of the delays to the dual fuel replacement Arran ferry Glen Sannox and her sister - Hull 802 - which were scheduled to be built due to enter service in mid-2018 but the calamitous contract has doubled in price - and is now estimated at £300m.

As the part-completed vessels languish in newly-nationalised Ferguson Marine in Port Glasgow, it is estimated they will not be finished until at least 2022 - four years late.

It comes as Arran islanders have demanded that the First Minister intervene saying that what is Scotland's busiest ferry crossing had suffered a "shocking" 50 days of disruption out of the first 70 days of this year.

READ MORE: Islanders' anger as safety issue brings Scotland's busiest ferry to a halt

The move has as ferry services came a standstill between Sunday and Thursday with multiple cancellations for safety reasons because of a fault with the ageing ferry's mooring equipment.

On Thursday all sailings on the route were wiped out as the First Minister expressed "great regret" over the state of the lifeline service.

Aboard the oldest ferry in the CalMac fleet

CalMac has said that a technical issue with the 27-year-old MV Caledonian Isles may well be resolved within days instead of six weeks, as previously predicted.

The "significant fault" which made the mooring winch gearbox unusable meant the vessel was "unable to safely berth during periods of adverse weather". But the taxpayer-owned ferry operator said that they had been able to source a suitable part to cut the impact on service.

Islanders have previously raised concerns over the £31 million project to reposition Brodick harbour by 90 degrees. It is claimed the new position has led to a spike in cancellations because it has made the high-sided vessels which serve the port more susceptible to easterly winds.

Arran Ferry Action Group chairman Gavin Fulton described the situation on the island as a "fiasco" adding: "The main problem across the network is that the boats are old and keep breaking down."

READ MORE: First Minister's "great regret" over state of Scotland's busiest lifeline ferry

He said there was a Scottish Government "failure to procure enough new boats" and that ministers were "playing politics with our lives".

He added: "Suffice it to say that the Arran ferry service is the worst it has been in living memory and is unlikely to improve any time soon unless someone in the Scottish Government takes decisive action now."

HeraldScotland:

Islay Community Council's ferry committee has raised its concerns about delays with ministers complete with a dossier of issues that have beset the route from the Argyll and Bute mainland hamlet of Kennacraig to the island.

It said that if there had not been the delays in building Glen Sannox and Hull 802, the replacement ferry might even have been place in 2022 - six years later than planned - but it now fears it will not be delivered until the middle of 2023.

In an analysis, the committee said: "We all know that some vessels are already near to or have passed their designated service times.

"These older vessels are already impacting costs, due to the regular need for repairs and CalMac is having to put extra millions of pounds into refit programs to help extend working lives.

"There is an obligation to meet the requirements of the Islands Bill and the National Islands Plan in terms of economic sustainability, assisting growth and development and halting population decline.

"The islands are potentially a huge source of extra income for government and much of this is not being fully exploited due to lack of capacity and resilience in the ferry service."

On March 23, two meetings will be held in Islay to discuss the requirements and specifications of the delayed ferry. They will be hosted by Caledonian Maritime Assets Limited (CMAL), the taxpayer-funded company which owns ferries and other infrastructure used by publicly-owned operator CalMac, which will also be represented with Transport Scotland officials.

Next year the island of Harris will have no ferry for three months because of upgrade work on the pier at Uig, Skye.

MV Glen Sannox launch in November 2017..but won't be operational till 2022

The Skye triangle route which connects Tarbert, Harris with Skye and Uist faces disruption as the pier at Uig is out of action in autumn, 2021.

The closure will last for around three months from September 2021 for a new linkspan to be installed and infrastructure upgraded for the delayed Hull 802 ferry.

A Scottish Government spokesman said:“We recognise the effect on those communities when there are unforeseen impacts on services due to weather or mechanical breakdowns.

“That’s why Transport Scotland is currently working with CMAL and CalMac to develop investment programmes for major vessels and small vessels with the aim of increased standardisation, taking account of the many and varied routes which CalMac serves.

"We have also been working for more than two years to find a resolution to the difficulties at Ferguson Marine with the completion of the two CalMac ferries, protecting jobs, and securing a future for the yard.

"The Scottish Government continues to work with CalMac, communities and business interest to ensure lifeline ferry connections are maintained and enhanced."

The spokesman said that it had led improvements that have helped drive passenger growth and CalMac now carries 5.3 million people (up 17.6% since 2012) and 1.4 million vehicles on an annual basis.