Hertfordshire County Council aims to repair dangerous potholes within one day of being alerted, data obtained by the RAC Foundation shows.
That's much slower than the most common response time of two hours, with the fastest councils in the UK acting within minutes.
Hitting a pothole, or even swerving to avoid one, can ruin a car's suspension, steering or tyres, according to the AA.
In extreme cases they can cause serious accidents.
In 2018, the AA estimated potholes cost drivers and insurance companies an eye-watering £12 million.
It said: "The pothole epidemic has become nothing short of a national disgrace."
A Freedom of Information request by the RAC found that Hertfordshire County Council uses a "risk-based" approach to fixing potholes.
Not only will a pothole's size be considered, but also the potential impact on road users and volume of traffic.
That means deeper potholes on quiet lanes will be less of a priority than minor defects on a major route.
On rarely-used roads, Hertfordshire County Council will only intervene when potholes are at least 10cm deep .
On busy major routes, potholes at least 5cm deep will be investigated.
RAC Foundation director Steve Gooding said: “The total number of potholes being filled in might still be limited by a shortage of funding, but this approach at least means those that are most dangerous are fixed first.
“Those particularly vulnerable to potholes – cyclists and motorcyclists – might ask whether the speed of pothole investigation should be based solely on the risk to users.”
For less dangerous potholes that are earmarked for specific repairs in Hertfordshire, patching up could take almost three weeks.
And the least troublesome defects may not be repaired at all - but the council will keep an eye on the pothole in case the problem worsens.
The Local Government Association called for more funding for council-controlled local roads.
Transport spokesman Councillor Martin Tett said: “Keeping roads safe for all users is one of the most important jobs councils do.
“That’s reflected in the fact that local authorities are fixing a pothole every 21 seconds."
He added that councils need "consistent and fairer government investment in local road maintenance".