Chancellor Rachel Reeves has warned petrol stations that they face serious consequences if they fail to update motorists on the latest petrol and diesel prices.
Labour's Fuel Finder tool is designed to show drivers the cheapest and most expensive petrol and diesel prices in their local area.
Petrol stations are required to report prices and the unavailability of fuel within 30 minutes of a change to petrol and diesel costs.
The scheme launched in February, but has been dogged by issues, including a lack of information, incorrect prices and a complicated layout for drivers.
Data included in the Fuel Finder is often used for price comparison tools, with the hope that drivers will be able to see the prices on map apps in the near future.
However, recent data from PA found that 1,751 fuel stations had most recently submitted a petrol price change more than a week ago.
Concerningly, 96 retailers had not provided an update to the scheme for at least a month, potentially resulting in drivers missing out on savings.
Commenting on the data, Chancellor Rachel Reeves, who has frequently praised the Fuel Finder tool, said it was "not right".
Chancellor Rachel Reeves said petrol stations were coming under the microscope of the CMA
|PA
She said the goal of the Fuel Finder scheme was to increase transparency among retailers and supermarkets, and drive down prices for drivers.
The Labour MP for Leeds West and Pudsey lamented the fact that some businesses were not submitting the latest fuel prices, meaning petrol and diesel car owners are spending more than they should.
She added: "I have given the Competition and Markets Authority powers to investigate, and they have issued hundreds of warning letters to businesses not complying.
"If these businesses continue to fail their customers by not reporting price changes, the CMA have assured me they will step in and issue fines."
LATEST DEVELOPMENTS
- M23 chaos: Driver arrested after fatal collision as Gatwick Airport issues urgent traffic warning
- Driver caught travelling at 116mph in 30mph zone as motorists rack up millions of speeding offences
- Donald Trump celebrates 'really big deal' as Toyota confirms $3.6bn Texas investment - 'Tariffs at work!'
Estimates suggest that drivers could save up to 6p per litre with Fuel Finder | PAThe CMA is able to issue forecourt owners and large businesses with huge fines if they fail to update Fuel Finder data.
It can impose a fixed fine of up to one per cent of worldwide turnover, a daily rate up to five per cent of daily worldwide turnover or a combination of the two.
The Petrol Retailers Association acknowledged that smaller, more rural sites may not update the Fuel Finder tool as frequently.
It put this down to these businesses not receiving deliveries of oil as often as larger chains, major retailers and supermarkets.
Most expensive petrol prices
Welcome Break Telford, Telford, Shropshire (TF11 8TG) - 182.9p
Ardminish Stores, Isle of Gigha, Argyll and Bute (PA41 7AA) - 181.9p
Welcome Break Birchanger, Birchanger Green, Essex (CM23 5QZ) - 177.9p
Hilton Park North and South Service Area, Wolverhampton, Staffordshire (WV11 2AT) - 177.9p
Shell Taunton Deane South, Taunton, Somerset (TA3 7PF) - 176.9p
Most expensive diesel prices
Welcome Break Birchanger, Birchanger Green, Essex (CM23 5QZ) - 197.9p
Welcome Break Telford, Telford, Shropshire (TF11 8TG) - 193.9p
Shell Magna, Swadlincote, Derbyshire (DE12 7AP) - 191.9p
Shell Hapsford MWSA, Hapsford, Cheshire (CH2 4QZ) - 190.9p
Oak Service Station, Dunmow, Essex (CM6 3LD) - 189.9p