England's roads have seen the number of potholes increase by almost a third in the past 12 months, research has shown.
A report from the Asphalt Industry Alliance (AIA) said there was an average of one hole for every 120 yards of road.
The group said it would take £8.5 billion and 13 years to put England's roads properly in order, while the time it would take to clear the pothole backlog on Welsh roads was around 15.6 years.
The nearly two million deep trenches dug into roads for utility and other works also reduce the lifespan of the roads and often lead to potholes, according to the AIA.
The number of trenches in each English local authority area averaged 13,212, while the figure for Wales was 4,613.
Last year saw nearly 800,000 potholes filled on English local roads, and almost 94,000 were filled in Wales.
As many as 74% of the local authorities in England, and 88% in Wales, believed there was a threat to road users' safety due to road maintenance under-funding.
The average cost to fill one pothole is £65, meaning it would cost £47 million per local authority to clear the problem.
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