British Airways has become embroiled in a row with Which? over the consumer group’s claim that the UK carrier emits up to 45% more CO2 emissions per passenger than rival airlines.

BA questioned the findings and described the research as “shoddy”, claiming the figures were several years out of date and inaccurate.

Which? Travel stood by the data which it said was up to date and provided by carbon analytics firm Flyzen and demanded the airline retract its “factually incorrect” response.

“We used the Flyzen calculator because it is impartial and considered a greater variety of factors to accurately estimate the carbon footprints of flights,” the consumer body said.

The BA statement said: “Which? only looked at 2% of our flights and their paid-for calculations, hidden behind a pay wall, are completely at odds with the figures calculated by the range of airlines they claim to have investigated.

More: BA in row over Which? emissions probe

“We are committed to net zero by 2050 and we are open to discussion on our approach to reducing our carbon emissions with anyone who is interested in accurate and robust data.”

Which? said the analysis found that one passenger flying from Heathrow to Miami with BA would be responsible for 1.13 tonnes of carbon.

This was almost a third more than the 860.9 kilos for the same flight with Virgin Atlantic, according to the study.

A BA flight from Stansted to Palma in Majorca emitted 160 kilos of CO2 per passenger, almost 50% more than Ryanair, Jet2 or Tui at 109.3 kilos on the same route.

An indirect flight from Heathrow to Singapore with Cathay Pacific was the worst case produced three quarters more emissions – 1.7 tonnes of CO2 – than the same journey with KLM at 958 kilos.

The example showed that connecting in Hong Kong with Cathay Pacific rather than Amsterdam with KLM means a couple more hours in the air, and therefore far more carbon being expelled, Which? said.

Which? travel editor Rory Boland said: “These figures show that swapping to a greener airline will allow the many of us concerned about climate change to immediately and significantly reduce our individual carbon footprint.

“If millions of us were to switch to a less polluting airline on our next holiday, it would bring pressure to bear on the worst polluting airlines and force them to prioritise their impact on the environment by introducing more efficient aircraft and cleaner fuels.”

A spokesperson for BA previously told Which?: “We are tackling climate change by developing sustainable aviation fuels and opting for greener aircraft.

“We are currently operating more than 40 new and fuel-efficient aircraft and have a further 73 on order. These are 25% to 40% more fuel-efficient than those they replace.”