FIREFIGHTERS will find it harder to tackle severe storms and terrorism unless a £400 million repairs backlog is addressed, financial watchdogs have said.

Caroline Gardner, Auditor General for Scotland, previously branded the backlog “insurmountable” as she warned fire engines are at risk of breaking down unless they receive tens of millions of pounds worth of investment over the next 10 years.

She said crews would find it tougher to respond to the changing threats facing society unless cash was found to maintain and improve equipment, vehicles and stations.

Insisting she was careful about the language used in her reports, Ms Gardner told the Scottish Parliament’s public audit committee: “I don’t use the word insurmountable lightly.”

Audit Scotland’s paper, released last month, said it was “unlikely” enough cash would be made available to deal with the backlog, with an average annual investment of £37.8m needed over the next 10 years just to prevent further deterioration.

Ms Gardner told MSPs: “The fire service rightly takes a very structured approach to maintaining its most important equipment and vehicles, so that people are safe.

“Things will go wrong from time to time – they’re bound to in any service. But at the moment we’re not seeing widescale problems because of a lack of maintenance.

“Those risks will increase if the lower level of capital investment isn’t made over the next ten years.

“But more importantly than that I think, because of the changing risks to the population because of the way we live our lives, because of an ageing population, because of the increasing number of severe weather events and the risk of terrorism, it’ll be harder to respond to those risks.”

She said pressures will be further increased because the current system of relying on retained firefighters and volunteers is “unsustainable”, particularly in the Highlands and islands where fewer people are signing up.

She added: “So to be able to have the right firefighters in place at the right time, and to make sure they have the equipment and vehicles that they need to be able to work effectively, requires a very significant amount of capital backlog. And the best estimate is the £389 million that we’ve used in the report.”

Ms Gardner said Scotland’s ageing population meant fewer people were fit enough to become retained firefighters, which requires working part-time and being on-call for long periods of time.

Audit Scotland's report praised the Scottish Fire and Rescue Service’s “strong financial management” but said it had inherited a backlog of repairs and investment worth £389m from the old regional forces.

If spending remains at current levels, auditors found this will reach £406m over the next decade and the “risk of asset failures, such as vehicle breakdowns, will increase significantly”.

To bring buildings, vehicles and equipment up to a “minimum satisfactory condition” would need an average annual investment of £80.4m over 10 years, while simply ensuring they don’t deteriorate further would require £37.8m a year.

It came after the Fire Brigades Union insisted firefighters and the people of Scotland had been “let down” by centralisation, with more than 1,000 jobs cut in the last five years.

Scotland’s single fire service was created in 2013 with the merger of eight regional forces, and has an annual budget of £296.9m.