Delivering his budget on Wednesday – only days before the UN climate conference gets underway in Glasgow – Sunak reasoned that making internal air travel cheaper by lowering the Air Passenger Duty (APD) would “cut the cost of living,” “boost regional airports” and “bring people together” from across the country.

“Right now, people pay more for return flights within and between the four nations of the UK than they do when flying home from abroad,” he said, adding that the lowered rates on flights between airports in England, Scotland, Wales and Northern Ireland will come into effect from April 2023.

The chancellor claimed the policy would benefit some “nine million passengers” who would “[see] their duty cut by half” as well as provide a fillip to airports like Aberdeen, Inverness and Southampton, which he described as “major regional employers.”

The announcement came a day after the government’s Climate Change Committee (CCC) issued an assessment of its ‘Net Zero’ strategy to curb carbon emissions by 2050. In the report, the advisory body had recommended bringing in policies to discourage “aviation demand” and warned the government that its strategy had “nothing to say” on aviation.

Noting that “most [carbon] emissions come from international rather than domestic aviation,” however, Sunak said he would create a new “ultra long haul band” of air passenger duty – affecting “less than 5%” of passengers – that would raise the cost of flights travelling over 5,500 miles, from April 2023.

Many social media users criticised the APD policy as flying “in the face of climate emergency” warnings, with a number of people noting that the move would “[worsen] air quality in the UK and beyond” since more passengers will “opt to fly.”

Environmental group Communities Against Gatwick Noise and Emissions (Cagne) was among those who called on Sunak to “[invest] in trains” instead.

In a series of tweets slamming the budget as an “utter failure,” Green MP Caroline Lucas said that the chancellor did not “get the memo on the climate emergency” and was “pouring fuel on [the] fires of ecological breakdown” while taking the UK “further away” from a greener economy.

Several people, including Labour MP and former Shadow Chancellor John McDonnell, questioned what kind of “message” Sunak was trying to convey ahead of the COP26 conference, which will see some 120 world leaders in attendance.

“So much for tackling climate change and fairness. Cutting air passenger duty on domestic flights undermines credibility before Cop26,” McDonnell tweeted, also pointing out that Sunak was “cutting the levy on the bankers who caused the economic crash in 2008”.

However, some commenters defended the move as prioritising the “domestic tourism market” over international travel. Others still opined that it would “force” train companies to lower their “too high” fares. A few people also claimed that domestic flights were a relatively smaller emitter than both rail journeys and international air travel.