Rachel Reeves has come under fire over the Government's new petrol and diesel scheme, which could cost drivers £260 a year.
The new Fuel Finder scheme was launched earlier this year to help drivers find cheaper petrol and diesel prices across the UK.
As part of the new rules, from February 2, forecourts were mandated to submit fuel price updates within 30 minutes of any change.
The initiative aimed to allow drivers to be able to see the cheapest petrol and diesel prices in their local area through the Fuel Finder service, which will eventually be available on sat navs.
However, a recent investigation by What Car? found that four out of five Government-recommended fuel finding apps showed out-of-date pricing.
This inaccuracy means drivers could be at risk of paying between 6p and 8p per litre of fuel more, equating to roughly £3.60 more for a tank of petrol and £4.80 for diesel.
The report also warned that drivers who rely on a fuel price app and regularly visit sites could end up paying £22 more each month and roughly £260 more yearly.
Chancellor Rachel Reeves has come under fire over inaccurate Fuel Finder reports
| GB NEWS/PAIn March, Ms Reeves shared: "My priority is protecting family finances and standing up for drivers, and Fuel Finder puts power back into their hands.
"By giving drivers the information they need to see where fuel is cheapest locally, they can avoid being overcharged and continue to fill up as normal. This is in addition to other steps we've taken to help households keep costs down."
The Chancellor had also promised the new fuel measures would save the average household £40 a year, including the extension of the fuel duty cut.
According to research, only one of the sites listed on the Fuel Finder was showing prices that had been updated on the day What Car? checked, in line with the new requirements.
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The Fuel Finder scheme hoped to help drivers find cheaper petrol and diesel prices
| PAPrices were checked for regular (E10) petrol, regular (B7) diesel and super unleaded petrol (E5) and found that the correct prices were only being displayed on Petrolprices.com.
The prices on four other sites, namely Confused.com, Fuel Finder UK, Fuel Spy and MotorMouth UK, were found to be displaying older prices in two of four locations.
In response to the findings, the Department for Energy Security and Net Zero explained that the navigation and price comparison websites and apps that use the data are responsible for displaying the information in a "timely manner".
The body noted that there may be a short lag depending on how frequently they refresh or process information.
The Fuel Finder scheme launched in February | PAA Government spokesperson said: "These conclusions are flawed and incorrect. Fuel Finder will play a crucial part in our work to tackle the cost-of-living head-on, with potential savings for households who own a car of around £40 a year at the pump."
Claire Evans, consumer editor of What Car? warned that more needs to be done to help "cash-strapped motorists".
"With fuel prices likely to stay eye-wateringly high for the foreseeable future, motorists need easy access to the latest fuel prices so they can save money wherever possible," she said.
The organisation has now called on DESNZ and the Competition and Markets Authority to act faster to enforce the legal requirement to provide up-to-date information and ensure the fuel apps are providing the latest information.