Climate campaigners and green experts have condemned the government’s decision to allow the drilling of the Jackdaw gasfield in the North Sea.

They said approval for the site would jeopardise the UK’s climate targets, fail to reduce the cost of living, and distract from the need to decarbonise the UK’s energy sector.

Many drew parallels with the record-breaking heatwave and drought, fuelled by global heating, that the UK experienced this summer.

“Is the prime minister living in a parallel universe? One where we haven’t just endured our hottest summer on record, with droughts, wildfires and, in all likelihood, the most heat-related deaths on record?” said Danny Gross, climate campaigner for Friends of the Earth. “And where the UN hasn’t warned that we’re on the brink of breaching the all-important 1.5C warming limit?”

As the gas from Jackdaw will be sold on international markets, Gross said it would not bolster the UK’s energy security, but would add to global greenhouse gas emissions. “The disconnect [between the government’s green ambitions and its actions] is maddening,” he said.

“This benefits oil giants and their shareholders and doesn’t make life more affordable as Burnham promised,” said Tessa Khan, the executive director of the campaigning organisation Uplift. “Clean energy is how we lower bills, reindustrialise regions and increase public control – not by caving to an oil industry making obscene profits while pushing up bills, laying off workers and driving the heatwaves we saw this summer.”

As the North Sea is a rapidly declining basin, any rise in jobs is likely to be small and short-lived, analysis suggests. Kyle Lischak, the head of UK at the legal pressure group ClientEarth, said: “The companies drilling our oil and gasfield will soon leave the empty oilfields with record profits, whilst we pay the price of extreme weather for decades to come.”

Ami McCarthy, the head of politics for Greenpeace UK, said: “Approving Jackdaw shows the toxic grip fossil fuel lobbyists still hold over our energy policy. Andy Burnham promised pragmatism, but there is nothing pragmatic about rubber-stamping a project that won’t lower energy bills, won’t boost energy security and will create just 27 full-time jobs.”

The Conservatives, Reform and some trade union leaders, including Sharon Graham’s Unite, cheered the government’s decision but 10 unions, representing firefighters, healthcare workers, teachers and others, signed a statement last week opposing development of the Rosebank oilfield.

Many Labour MPs have been sorely disappointed by the government’s green light, but some are seeking a compromise by which in return for staying quiet over the Jackdaw decision – and potentially over the Rosebank oilfield, a decision on which is still in the offing – they want to stave off any watering down of the mandate on electric vehicles, which is also under consideration.

“The EV mandate is a bigger issue, in terms of emissions in the long term,” one Labour MP told the Guardian.

But the Green party sees a potential electoral advantage in Labour’s divisions over the North Sea. There are now scores of seats in which the Greens could be the main opposition to Labour at the next election, and where concern over the climate is a key priority. The Green party leader, Zack Polanski, said of the Jackdaw decision: “This is climate vandalism. Today’s decision by Labour is a betrayal of all of our futures, Labour has abandoned all credibility in the fight against climate change.

“The energy secretary [Miatta Fahnbulleh] has herself said it will make no difference to energy bills; the health secretary has admitted the summer heatwave added to pressure on the NHS, and the industry’s own assessment is that it will create only 27 jobs. This is a victory for Shell over the people.”

Burnham and Fahnbulleh are expected to attend the next UN climate summit, Cop31, in Turkey next month, where governments will be asked to show they are living up to their climate commitments.

Mohamed Adow, the director of the Power Shift Africa thinktank, warned that the UK’s power to persuade was damaged by further fossil fuel exploitation, which would encourage other countries to ignore climate science and pursue markets for their own reserves.

“Approving Jackdaw is a serious blow to Britain’s international climate credibility,” he told the Guardian. “The UK cannot expect developing countries to move away from fossil fuels while giving the green light to new drilling in its own back yard. That double standard will not go unnoticed by countries already suffering the consequences of climate change.”

He added: “Britain has spent years presenting itself as a climate leader, but leadership is about what you do, not what you say. At a time when the world urgently needs to reduce its dependence on fossil fuels, approving new gas developments sends completely the wrong message.”