Councillors and officials are embroiled in a fierce dispute over the design of the £2.7 million Stranraer marina, key components of which are said to be unfit for purpose.

Dumfries and Galloway Council has produced a masterplan for the historic harbour, designed to attract leisure craft to a town struggling to recover from the relocation of the Stena Line ferry terminal to Cairnryan.

But a group of local councillors led by independent Willie Scobie has questioned the design of the facility, which he claims was changed without proper consultation from the plan originally proposed. Scobie, who has raised the issue with Audit Scotland, says the marina’s slipway is “in the wrong place” and therefore unusable at low tide, while, separately an intended boat crane will impede the operations of commercial fishermen, the traditional harbour-users.

The local councillors and other objectors also claim that the council has had to hire earth-moving operators to clear sand and shingle off the slipway whose siting on the beach makes its usability “dependent on too many variables” related to the natural movements of the beach.

Scobie said: “We asked for an investigation into the changes of specification and we still have not been told who was responsible. Under a process they call ‘value engineering’ unaccountable officials reduced the cost of building a slipway from £1.12m to £600,000. But the savings have rendered it fit only for dinghies on trailers and not by yachtsman of the sort the marina is supposed to attract. It’s therefore a waste of £600,000 even before you add in the cost of shingle, around 15,000 tonnes of which has been removed. If it wasn’t so serious it would be funny.”

The council is employing a consultant engineer to review the works, due to report in September. But Scobie said: “The fact that this person is doing it for free raises questions about the integrity of the process.”

A spokesman for Dumfries and Galloway Council said: “The [original] plan referred to was a schematic illustration, intended to serve only as an indicative idea during the emerging design stages. The final siting of the boat lift was based on technical surveys to assess suitable access, ground conditions for structural foundations, close proximity to the boat yard and ease of access to water-borne boats in the harbour.”