The Scottish Government has spent £16 million in less than four years on design and assessment for work on a beleaguered stretch of road.

The Rest and Be Thankful on the A83 in Argyll and Bute has been blighted by landslips in recent years, forcing ministers to explore long and medium-term fixes.

Last year, it was agreed a shelter would be built above the road to protect it and passing cars from debris caused by landslides, while a medium-term solution will see cars use the adjacent Old Military Road.

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According to figures provided to the Scottish Tories by Transport Secretary Fiona Hyslop, just in excess of £16 million has been spent on design and assessment, with nearly £5 million spent between the beginning of this year and August 16.

“The Scottish Government is committed to delivering medium and long-term solutions to address the landslip risks at the A83 Rest and Be Thankful,” she said in response to a written question in Holyrood from Scottish Tory MSP Tim Eagle earlier this week.

“Delivery of a permanent and resilient solution is a priority and we will continue to seek ways to achieve that as quickly as possible.

“Following identification of a preferred option last year, the next step for the permanent solution, which is the detailed development and assessment of the preferred option, is progressing at pace and will conclude with the publication of draft orders for comment, currently expected by the end of this year.

“As with all infrastructure projects, delivery of the scheme can only commence if approved under the relevant statutory authorisation procedures and thereafter a timetable for construction can be set.

“At the same time, improvements to the existing Old Military Road through the Glen Croe corridor are being made to make it a more resilient diversion route until the long-term solution is in place.”

Mr Eagle denounced the “eye-watering” figure “before a spade has even hit the ground”.

He said: “Motorists have suffered misery on this key route for far too long but there still appears to be no end in sight despite all of this money being spent.

“I am pleased a preferred solution has finally been found after years of dither and delay, however the SNP government must ensure that spending doesn’t spiral out of control, as we have already seen with other projects.

“The constant closures and diversions that motorists are having to put up with are causing significant harm to the local economy the longer they go on.”

Transport Scotland announced in July the award of a £5.5 million contact for ground investigations ahead of work on building the shelter.