Rishi Sunak has defended cutting domestic flight taxes in the run-up to next week’s Cop26 summit, after being accused of going “headlong in the wrong direction” about tackling climate emergency at a pivotal point for Britain. Labour said it was an “astonishing” announcement from the chancellor in Wednesday’s budget, given the UK government will urge many world leaders, set to arrive in Scotland within days, to speed up decarbonisation plans in their own countries. Sunak halved the tax on domestic flights, which are already far cheaper and more polluting than train journeys. Air passenger duty was increased by £4 on “ultra-long” flights of more than 5,550 miles, from £87 to £91. Overall, the changes were a tax giveaway of £30m a year. After criticism from environmental groups, the chancellor batted away claims it could lead to 400,000 more domestic flights every year. “What we’re doing on air-passenger duty is going back to a system we used to have, which means we don’t essentially double-tax people for flying inside the UK – so in that sense it’s a pro-union policy,” Sunak told BBC Radio 4’s Today programme. He said the new ultra long-haul band was fair because it meant “the further you’re flying, the more emissions, then you will pay a higher rate”. Sunak was asked why he did not simply increase the levy for longer haul flights and leave domestic air-passenger duty at its current level, instead of cutting it significantly. “We could have done, but we wanted to deliver on a previous commitment to reform air-passenger duty to return to the system that we used to have so people flying within the UK are not taxed twice, which we never thought was right,” the chancellor said. “It supports the union, it supports regional airports, which are big employers. But also aviation in general only accounts for about 7-8% of our overall carbon emissions and, of that, I think domestic aviation is less than 5% – so it is a tiny proportion.” Asked if the UK should be showing moral leadership on the issue, given it will be pressing other countries to drastically increase their commitments to tackling climate change by trying to limit global warming to 1.5 degrees, Sunak said: “We’re a country that has decarbonised faster than basically any other advanced nation over the past 10, 20, 30 years, so I think our track record on this is pretty good, actually. “In my small responsibility on the finance side, last week the UK was named the world’s best place for green finance anywhere in the world … I feel pretty confident about our leadership on this issue.” However, the shadow chancellor, Rachel Reeves, who stood in for Keir Starmer in the Commons on Wednesday after he had tested positive for Covid, said: “We wouldn’t have gone ahead with that cut. “I find it astonishing that the week before Cop26, when we are supposed to be showing global leadership, we have cut air-passenger duty on domestic flights. We should be encouraging people to use our train network for those journeys, not cutting APD on domestic flights.” She added: “If you’re a banker on a short-haul flight sipping champagne, you would have been cheering at the budget yesterday. If you’re on a modest income and you’re worried about the rising cost of living, frankly there was very little to cheer.”