A FERRY service branded 'useless' by campaigners fighting for the return of robust vehicle-carrying ships has racked up more than 4,500 cancelled sailings in the last three-and-half years.

The lightweight foot passenger only vessels run by Caledonian MacBrayne on the Gourock-Dunoon route have been labelled 'not fit for purpose' by past Scottish Government ministers.

But current connectivity boss, Paul Wheelhouse, has kept the weather and breakdown prone boats operating, amid plans to plough public money into potentially keeping them going for years to come.

The Telegraph can reveal that engine and propeller replacements for MVs Argyll Flyer and Ali Cat have been proposed despite their thousands of failures to sail — which have come about mainly because they can't cope with windy weather.

Between January 1 2016 and June 30 this year the vessels — dubbed 'bathtub boats' by some fed-up passengers — have had 2,823 services cancelled due to 'adverse weather'.

A further 1,646 called-off sailings were put down to 'technical' hitches with the small craft.

In the first six months of this year alone there have been 678 failures to sail — equivalent to 113 cancellations every month.

Forty services were cancelled due to 'other' reasons across the overall period since 2016.

Meanwhile, larger vehicle-carrying vessels operated by Western Ferries between McInroy's Point and Hunters Quay run at near 100 per cent reliability.

When asked about engine and propeller replacements for the vessels, CalMac confirmed that this was 'planned future work'.

Their spokesman said: "It's to be undertaken over the medium term — next two to three years."

A £50,000 expert report commissioned by the government in 2013 ago recommended ships of at least 40 metres in length.

But successive ministers — including first minister Nicola Sturgeon when she was infrastructure secretary from 2012 — have consistently failed to deliver improvements to the service.

Ms Sturgeon chaired a dedicated ferries steering group involving campaigners and councillors at a time when it was the declared 'wish' of ministers to bring back car-carrying vessels.

The Dunoon-Gourock Ferry Action Group is demanding no further delay in implementing the recommendation of specialist transport consultants MVA for 40-metre long ships.

They argue that vessels of this size must be able to provide a vehicle service in order to make them economically viable and provide a return to the public purse for the cost of building them.

In a letter to scrutiny body Audit Scotland, the Dunoon-Gourock Ferry Action Group described the current service as 'useless'.

Ken Barr, of the action group, said: "Nicola Sturgeon, when she was the cabinet secretary responsible for ferries, said that the status quo was not an option.

"But here we are years later still facing the same issue and no realistic decision as to the future.

"She also said, when pressed, that it was the 'policy' of the Scottish Government to have a vehicle and passenger service on the route.

"This has been consistently blocked by the civil servants in Transport Scotland. Why?"

Mr Barr added: "If proof were needed that these vessels are unfit for purpose, then I point to the fact that they cancelled more times in their first three months of service than the previous car ferries had in 40 years — and they never once had to cancel for a whole day.

CalMac did not respond to a request for comment on the level of cancellations.