Financial help from taxpayers to airlines hit by the coronavirus crisis must come with strict conditions on their future climate impact, the former EU climate commissioner and a group of green campaigners have said.

“It must be conditional, otherwise when we recover we will see the same or higher levels of carbon dioxide [from flying],” said Miguel Arias Cañete, the EU climate commissioner who led the bloc to the Paris agreement, in an interview with the Guardian. “We know the level of emissions we have to commit to [under Paris]. They [airlines] are worried about survival and will need lots of support, lots of liquidity – that gives them a big responsibility.”

A group of 26 civil society groups in the UK have written to the chancellor, Rishi Sunak, demanding “stringent conditions” on any rescue, including strict targets on greenhouse gases in line with the Paris agreement and measures to help workers. “Public money must be used to address social and environmental priorities, as well as economic needs,” they wrote.

Aviation has all but ceased in some countries and flights are vastly down in most others, owing to the lockdowns and other suppression measures. Airlines have been appealing to governments for bailouts as fleets have been grounded.

But campaigners and experts fear that after the Covid-19 outbreak has waned, the sector could bounce back with the aid of public money and send emissions soaring.

In their letter to the chancellor, the campaigners – including Greenpeace, Flight Free, the IPPR and New Economics Foundation thinktanks, and Tax Justice – call for the government to take equity stakes in airlines rather than handing out cash or loans. They want to see social benefits with workers’ rights enforced, including a living wage and no mass redundancies a condition of any rescue. In the longer term, they want to see support for a “just transition” for workers to move to jobs in lower carbon industries.

They also want a new fiscal regime that includes a frequent flyer levy or air miles levy, replacing air passenger duty, which would reduce demand without removing access to flights from those with limited alternatives or limited resources, by shifting the tax burden to frequent leisure flyers. About half of people in the UK do not fly in any given year, but 1% of people take a fifth of all flights.

Rebecca Newsom, head of political affairs at Greenpeace UK, said: “Emergency funding must be used to tackle emergencies, not to support business as usual. Conditions are needed to protect workers’ rights, prevent public money from being diverted into the pockets of shareholders, and reduce demand gradually over time through a frequent flier levy, so that the sector operates within safe limits for the climate.”

Attaching conditions to any bailout could take several forms. Cañete wants to see a carbon tax or emissions trading system such as the one operating under the EU. “Market mechanisms are needed,” he said.

Airlines UK, a trade body, said the industry was already taking steps to reduce their environmental impact before the coronavirus crisis hit. “The UK aviation sector has already committed to achieving net zero carbon emissions by 2050 – the only national aviation industry to do so,” said a spokesperson. “This will be achieved via a range of measures, including airspace modernisation, the development and commercialisation of sustainable aviation fuels, new cleaner planes, and the UN carbon offsetting scheme Corsia.”

Airlines face difficult choices ahead. More efficient aircraft will help to reduce emissions, but the impact will be limited. Biofuels offer a possible answer, but they are still expensive and there are difficulties in ensuring that the sources are environmentally sustainable. Electric planes are still some way in the future, and solar-powered flight a distant dream.

“We need to stimulate research and development into things like hydrogen fuel,” said Barbara Buchner, managing director of the Climate Policy Initiative. “We need more proactive thinking from airlines – they can’t imagine we will go back to the way they were before.”

The coronavirus disruption may also bring about permanent changes in people’s habits, some experts hope. Business flying has stopped meetings from happening, but people have found ways to work with video conferencing and other cheap technology, forcing businesses to question whether their staff need to fly as much in future.

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“We are not flying as much – why not keep not flying?” asked Kevin Anderson, professor of energy and climate change at Manchester University. “Why not reinforce the good things that are coming out of Covid-19?”

One effect of the coronavirus crisis has yet to be felt. Under the Corsia (Carbon offsetting and reduction scheme for international aviation) system adopted by the International Civil Aviation Organisation, airlines would have to curb their future emissions using efficiencies, alternative fuels and offsetting, such as investing in forests, renewable energy or other carbon-cutting projects.

Before the coronavirus crisis emerged, airlines pushed for the average emissions in the years 2019 and 2020 to be used as the baseline by which future emissions would be judged. In any years from 2021 onwards, when emissions from the sector exceed the average of 2019 and 2020, the difference between actual emissions and the baseline will have to be offset, meaning airlines will have to buy carbon credits from carbon-cutting projects.

Choosing 2019 and 2020 should have made those targets easy to meet for airlines if air travel had continued to rise this year as it has in recent years. With the Covid-19 pandemic, however, the disruption to travel means emissions are likely to be drastically lower than envisaged for 2020 – meaning Corsia’s future carbon targets will be much tougher for them to reach, if the scheme goes ahead without changes.