Further threat ferry fiasco ships may never be delivered as cost to taxpayer soars by nearly £100m

It says challenges are lack of manpower, potential design changes and the fact that materials bought some time ago are "not fit for purpose".

New figures from Ferguson Marine now show that the costs are now forecast to soar by nearly £100m from around £240m to nearly £340m.

Scottish Government-controlled ferry owners Caledonian Maritime Assets Limited (CMAL) has warned that the level of unprogrammed work involving Glen Sannox remains "unquantifiable" and "continues to be a significant risk to the project".

CMAL says there is a "slippage" in the commissioning of Glen Sannox and that unless action plans are "very effective cost and scheduling targets are unlikely to be achievable in line with the current date constraints".

A series of regular calls are now being arranged between deputy first minister John Swinney and Ferguson Marine.

In a separate update to the Scottish Parliament, Ferguson Marine chief executive David Tydeman has said that the two ferries will be subject to further delay.

Issues with building the ferries mean that Glen Sannox was originally not to see service till between March and May 2023 at the earliest, while Hull 802 was not due to set sail till between October and December 2023.

Now Mr Tydeman has said that moving resources to deal with issues with Glen Sannox means that a handover of Hull 802 is not now planned until the first three months of 2024 while there was a "one or two month worst case slippage" with the other vessel.

Glen Sannox and Hull 802, which are due to serve the Clyde and Hebrides ferry network are already over five years late while costs have risen by at least two-and-a-half times from £97m to £250m.

One ferry user group official said that the continuing issues "chaos amidst chaos" saying that ministers must come up with a "realistic" view on if and when the vessels will be delivered.

In a new August analysis, CMAL has warned that nationalised Ferguson Marine have not considered the "significant threats" posed by the continued risk of late installation of cables in a May risk register.

It said that consideration is only given to the reinstatement of nearly 17 miles of cables removed from Glen Sannox in February.

But it said "no consideration" was still not given to the main body of cable installation that extended ship-wide totalling 125 miles.

Completion rate of cables was at 26% against a target of 65%.

"The current rate at which cable is pulled presents a serious threat to the project," CMAL said.

It said the same concerns extend to the threat posed by the time scale to manufacture and install remaining pipe parts needed to complete the essential systems of Glen Sannox.

One of a list of key challenges for the shipyard according to CMAL includes completion of pipework to meet commissioning dates.

Others included closure of design gaps, availability of experienced supervisors and materials, shortage of experience tradesmen, delivering and completing production drawings and a "lack of familiarity with final stages of finishing the vessels, surveys, documentation and certification."

The CMAL analysis says: "Ongoing design changes affecting the constructability of the vessels' design are driven exclusively within the shipyard process to meet regulatory and contracted specification requirements and are not driven by CMAL request for change. "All are related to outstanding technical queries and previously unidentified works. Closure of final design gaps is needed, which at this late stage of the project remains a significant risk to the project."

According to Ferguson Marine's July traffic light system of analysis there is also a 'High' code red concern over a risk that items are delayed to the yard from the supplier and that there is a "lack of buy-in from the workforce to deliver the plan".

CMAL was also of the opinion that the risks to Glen Sannox not satisfying deadweight design requirements "are significant" as this would reduce the designed cargo carrying capacity.

CMAL, which owns the ferry fleet and much of the infrastructure, also said there was a review under way by Ferguson Marine over the progress of Hull 802 saying that "lessons learned during the construction phase of Glen Sannox are not trickling through as a more robust pre-outfitting block stage build philosophy".

It said that it is participating in design reviews on Hull 802 and are updating the outfitting strategy, pipe, insulation and electrical installation plans and start dates.

It warned:"A detailed review of Hull 802 is currently underway, involving technical input from the yard, CMAL, and the principal design contractor. We would point out that this level of review is not considered in the current programme, and neither is the time frame needed to produce revised construction drawings.

"It is unclear what level of change can be successfully implemented without negatively impacting the cost of finishing the vessel or jeopardising the agreed-upon delivery date."

Kate Hall of the Scottish Government's strategic commercial assets division has told Mr Swinney, business minister Ivan McKee and transport minister Jenny Gilruth that Ferguson Marine and CMAL were "engaging frequently and openly", adding: "Challenges exist but they are being openly addressed."

She added in a memo: "There continues to be significant risk to the costs of the project as the level of un-programmed work remains undefined, and unquantifiable at this stage.

"The financial assurance work is ongoing by [Ferguson] and costs and programme for each vessel are being tested and reviewed by the senior management team of [Ferguson].

"The ongoing detailed review by [Ferguson] is examining the of the scope of work for each of its key subcontractors, assessing materials and equipment still to be purchased and interrogating the man hours of both the direct and subcontract labour required to complete the vessels to the agreed programme."