Warrantywise compared data from the SMMT showing the top 10 registered vehicles in 2024 with its own data for repair costs under warranty.
It found that for the data available to compare, on average repair costs were up 20%.
The model most impacted was the Vauxhall Astra with a 28% increase in repair costs.
Second was the now discontinued Ford Fiesta, which was the most popular car registered in 2024, with a 25% increase in repair costs.
Antony Diggins, managing director of Warrantywise, said: ‘Our latest Reliability Index data from 2024 reveals some key trends for car owners to be aware of.
‘With repair costs continuing to rise, it’s something all motorists will need to consider – especially given the wider economic challenges and inflation in the UK.
‘Looking at the most popular choice of used car from 2024 to 2025, our reliability data highlights the importance of making informed decisions when buying second-hand.’
He added: ‘That said, our data offers valuable insights for anyone looking to buy a used car or wanting to understand the potential repair issues with their current vehicle.
‘It is also a reminder that cars are complex machines, even the most reliable ones can develop faults – no vehicle is completely immune.
‘We urge drivers to check the latest Reliability Index from Warrantywise if they’re looking to buy a used vehicle, to give a real-world indication on reliability.’