Repairs to fix Scotland's pothole-blighted roads are facing a £3bn backlog of work yet to be completed, according to a Holyrood committee.

More than a third of local streets and 13% of major roads need work done, the Rural Economy and Connectivity Committee found, with their condition set to worsen if more money is not spent.

Scotland's transport secretary is now facing calls to develop a national strategy backed by "substantial additional investment" to repair and improve roads across the country.

In a letter to Michael Matheson, committee convener Edward Mountain said the backlog for trunk road repairs is currently £1.2bn, in addition to an estimated £1.8bn for local roads.

Mr Mountain cited Audit Scotland reports about road repairs showing there has been a 26% decline in spending on local roads in a five-year period and "significant maintenance backlogs", with local authorities also reporting a 7.5% drop in funding over the same time.

Commenting on the findings, Mr Mountain said: "The committee is concerned that there is an estimated £1.2bn backlog for maintenance of trunk roads, the main arteries of Scotland's roads network, and around £1.8bn needs to be spent to bring the local roads network up to a satisfactory standard.

"While the committee acknowledges the pressures on local government budgets, it is clear that not enough has been spent on local roads over a number of years.

"Evidence heard by the committee also suggests that current expenditure levels will be insufficient to prevent an ongoing deterioration in the condition of roads across Scotland.

"That is why the committee is agreed that a new approach is needed to make significant inroads into addressing the accepted maintenance backlogs and ensure that, moving forward, road maintenance is appropriately managed and resourced so that the roads network is truly fit for purpose."

Scottish Conservative transport spokesman Jamie Greene said: "These figures are a damning indictment on the SNP's failure to manage our roads network.

"Now, after 12 years of Nationalist neglect, Scotland has £3bn of repair backlogs and 150,000 potholes.

"Our roads are the worst in the UK and in a state of chronic decline - cracks and potholes are now becoming the norm.

"It's clear that the current approach is not working and unless the SNP changes course our roads network will continue to deteriorate."

A Scottish Government spokesman said: "The most recent Audit Scotland report found 87% of trunk roads are in an acceptable condition.

"We are making significant efforts to maximise every penny that is spent on maintenance and our Road Asset Management Plan sets out how we prioritise maintenance and ensure cost-effective use of resources.

"The budget for maintaining roads Transport Scotland looks after has increased by more than £33m in 2019-20."

He added: "The Strategic Transport Projects Review (STPR2) is currently underway and will identify the strategic transport interventions required to provide Scotland with a network fit for the 21st century and will inform Scottish ministers' investment decisions for the next 20 years."