The official range of the electric Kia e-Niro has been downgraded after the firm discovered a external test agency hadn't followed correct procedures for the Worldwide Harmonised Light Vehicle Test Procedure (WLTP).

As a result, the higher-spec 64kWh e-Niro now has an official range of 282 miles rather than 301 miles, while the 39.2 kWh e-Niro is rated at 179 miles rather than 193 miles.

All new cars to be sold in the European Union are subject to the WLTP test procedure, which was introduced this autumn. Kia says that the independent organisation overseeing the test process accidentally provided an incorrect testing methodology and then approved the results it generated.

This led to the e-Niro being tested for a disproportionate length of time on the WLTP urban cycle, comprising lower overall vehicle speeds and a reduced energy requirement, resulting in an over-estimation of the vehicle’s all-electric range.

Kia itself then discovered the wrong result during ongoing homologation work for another new Kia electric vehicle.

The firm is now contacting customers who have bought the car - which doesn't go on sale in the UK until early 2019 - to explain the changes.

It is not currently clear if the related Hyundai Kona electric, or any other vehicles tested by the agency, will be similarly effected.

In independent Real Range testing by What Car?, conducted on its own test route, the 64kWh Kia e-Niro achieved the second equal highest range of any electric car to date, recording a range of 253 miles. That was matched by the Jaguar I-Pace.

The Hyundai Kona recorded the highest Real Range, at 259 miles.

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