A report on the performance of UK mobile operators that named Vodafone as having the poorest overall network performance of the country’s four operators has drawn strong criticism from the firm.

Network performance monitoring specialist RootMetrics published its UK mobile network performance review on Thursday, ranking Vodafone in last place for network reliability, mobile internet performance, and call and text performance. Vodafone was ranked third of the four for network speed, with 3UK ranked as having the slowest network.

Vodafone rejected the suggestion that it has the worst UK network performance and said in a statement that it believes Root Metrics’ testing process “does not appear to follow standard industry practices” as well as questioning whether the measurement firm was “fully impartial”.

Root Metrics said that the research was not sponsored by one particular mobile operator, saying only that its data is available to all the major mobile operators. The firm said it has signed NDAs “precluding us from naming the companies that we are working with.”

UK LTE leader EE was ranked in first place across all metrics, a position it publicised in a press release on Thursday morning in which it described Root Metrics’ testing as “rigorous” and “independent”. CEO Olaf Swantee said:

“Today’s results show that the EE network gives customers everywhere in the UK the best mobile experience. This is down to our ongoing investment in introducing 4G, increasing 3G capacity and upgrading 2G, while also spending hundreds of millions on phone call quality. We encourage the most rigorous independent testing of mobile networks in the UK, and strive to set new standards in performance and reliability.”

Vodafone, which went live with its LTE network in August last year, further criticised Root Metrics, however, saying that it believes that some of the data used “may well be over six months old”.

“The evidence we have seen of how Root Metrics conducted some of its tests leads us to believe that they were carried out in an inconsistent manner,” read a statement sent to Telecoms.com by Vodafone. “Those looking for more robust research should be approaching more established researchers, such as Ookla, who are completely independent and use hundreds of thousands of real, unbiased customers across the country for their results.”

“We cannot take the results of this report seriously and neither should our customers.”

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Vodafone UK is not the only operator to hit out at Root Metrics having been given a poor ranking in its reports. A US version of the report was published last week, and found that T-Mobile USA scored similar results to Vodafone in the UK, ranking lowest on network reliability, mobile internet performance, call and text performance but beating rival Sprint to third place in terms of network speed.

T-Mobile USA CEO John Legere took to Twitter to question the reliability of the data used in the test.

“The data from @rootmetrics #1yearlater might still be true for our competitors, but when you move as fast as @TMobile – it’s #oldnews,” he tweeted. “Congrats to our competitors –you guys really knocked it out of the park on that report, LAST year when the tests were done. #uncarrier #BGR.”

“We’ve said it before, but I’m happy to say it again. We look at REAL results from REAL people when we make network claims. #uncarrier.”

RootMetrics said that its report offers an “unbiased, transparent characterisation of UK mobile performance from a consumer’s perspective”. The firm added that during its testing of UK networks, the firm drove more than 23,000 miles and collected more than 840,000 samples, which it claims represents approximately one sample for every 100 mobile phone contracts in the UK.

The firm said that it used handsets bought off-the shelf to test outdoors, during driving and at over 1,000 indoor locations.

“These results give UK consumers and businesses the most accurate view of mobile performance in the UK that has ever been made available. From nation to neighbourhood, people now have access to data showing them the best network in their area,” said RootMetrics CEO and President Bill Moore.

“No other study of this size and scale for mobile performance has ever been carried out before in the UK, and it has, for the first time, shown consumers the true services they are receiving from their network provider.”

In November last year, Vodafone was criticised by UK regulator Ofcom for failing to meet the coverage obligation attached to the 3G licences awarded in the country’s spectrum auction in 2000. The operator was required to provide coverage to 90 per cent of the UK population by June 30^th 2013 but had only covered 88.66 per cent of the population by this time. However, Ofcom announced in February this year that Vodafone has now met its requirements.