The proportion of Norfolk's major roads rated as being in poor condition has almost doubled in the space of three years.
New Department for Transport figures show 7pc of the county's A-road network are currently classified as being in the worst category, up from 4pc in 2024.
Over the same period, the conditions of the county’s smaller roads has also worsened.
B and C roads judged to be in poor condition rose from 6pc to 7pc, while the figure for unclassified roads increased from 6pc to 8pc.
Officials at County Hall said funding and buying power were not keeping pace with the rate at which roads were deteriorating.
Councils have to carry out regular surveys of road surfaces under their management and categorise them as red, amber or green, with red meaning the roads are "poor" and should have been considered for maintenance.
Norfolk was among some 45pc of councils which reported an increase between 2024 and 2026 in the proportion of A road classed as red.
The figures refer to the amount of road length, not the number of roads.
A spokesman for the council, which is run by Reform, said: "Norfolk uses the nationally recognised Surface Condition Assessment of the National Network of Roads survey to assess the condition of classified and unclassified roads.
"Results show a modest deterioration in road condition, reflecting the challenges of maintaining a large rural highway network alongside increasing traffic demands and rising costs.
"Norfolk's strategy focuses on preserving roads and Norfolk delivers significant levels of preventative maintenance.
"Treatments like surface dressing extend pavement life, delay costly reconstruction and reduce numbers of reactive repairs.
"Norfolk's approach contributes to relatively low pothole numbers per mile and a positive result in the National Highways and Transport satisfaction survey, having ranked in the top three of similar councils for the last six years."
Norfolk County Council is responsible for about 6,000 miles of road, but not the A11 or A47, which are in the hands of National Highways.
Across England as a whole, 4pc of local A road was categorised as red in 2026, which meant Norfolk's 7pc outstripped the national average.
Luke Bosdet, from the AA's motoring policy unit said: "The road condition report once again reveals two different Englands: one with major and main roads in reasonably good condition and another with minor and rural roads often pitted with holes and defects.
"Many of these defects don't quite meet a council's criteria for repair but still pose a threat, or are bad enough to meet repair requirements but are back-logged on a long list.
"What is happening on rural roads partly mirrors what is happening in residential streets but is ramped up to a higher threat level: potholes and other defects are harder to spot, more severe and take even longer to be repaired."
Earlier this year, it was revealed it would cost more than £71m to clear the repair backlog to bring the county's roads up to scratch.
Reform's budget proposals to help plug a £36m funding gap include saving £475,000 by reducing highways maintenance activities by 5pc and reducing grit runs and highways treatment to save £225,000.
Those proposals have been criticised by opposition councillors. Kay Mason Billig, Conservative group leader, said: "You cannot spend months promising better roads and then quietly take money out of maintaining them."
The Reform administration has been trialling new maintenance methods, including a specialist repair treatment called Roadmender to fix potholes, cracks and other defects and the JCB Pothole Pro machine.
Tom Dickerson, the council's cabinet member for highways and transport, has said exploring such technologies could help find ways to maintain roads more effectively and deliver better value for Norfolk residents.
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