Sadiq Khan has urged Andy Burnham's government to recommit to net zero and to keep cutting Britain's reliance on oil and gas, in an intervention that lays bare the first significant public split between two of Labour's most senior figures.

Writing in the Guardian on Saturday, the mayor of London said the new administration must make clear it will continue to reduce the country's dependence on fossil fuels "to get Britain back on track", as the UK endures a summer of drought, wildfires and heatwaves. He said the "terrifying scenes" of recent months showed the world had entered an "era of extremes".

"National governments across the globe must step up and meet the gravity of this moment with renewed focus, funding, and resolve."

The timing is pointed. A decision on whether to approve drilling at the Rosebank and Jackdaw fields in the North Sea is expected within weeks, with the public consultation on Jackdaw closing on 10 August and Rosebank on 17 August. Both are run by the Offshore Petroleum Regulator for Environment and Decommissioning, which refers the projects to the secretary of state for a final ruling.

Burnham, who was appointed prime minister on 20 July after winning the Makerfield by-election in June, has so far declined to say which way he will go. Last month he said he would be "pragmatic" about oil and gas and that decisions would be made "in due course", adding: "The question isn't whether Britain will still be using oil and gas, the question is where does it come from."

That marks a shift in tone from his years as mayor of Greater Manchester, when he backed the proposed fossil fuel non-proliferation treaty, describing it as a "lifeline" that "all governments" should join, and supported the Climate and Nature Bill.

The two fields have a long and contested history. Jackdaw, a gas condensate field 150 miles east of Aberdeen, was first approved in 2022; consent for Rosebank, west of Shetland, was granted in September 2023. Both approvals were ruled unlawful by the Court of Session in Edinburgh in January 2025, after judges found ministers had failed to account for the emissions produced when the extracted fuel is burned — a requirement established by the Supreme Court's Finch judgment in June 2024. Lord Ericht suspended the quashing orders pending fresh decisions, allowing preparatory work to continue.

Adura, the joint venture between Shell and Norway's state-owned Equinor that now holds a majority stake, submitted revised assessments in June and says more than £3bn has already been invested. It argues the two fields could together supply about 10% of UK natural gas production, with Jackdaw alone providing enough gas to heat 1.4 million homes.

David Whitehouse, chief executive of Offshore Energies UK, said: "UK oil and gas is energy we have control over, produced in our own waters under our own standards. It is a strategic asset."

Campaigners dispute the benefits. Tessa Khan, executive director of Uplift, said Rosebank "won't take a penny off our bills or meaningfully boost UK energy supplies — it's overwhelmingly oil for export", noting that around 90% of its reserves are oil bound for international markets. Robin Wells of Fossil Free London called reports that Burnham might approve the fields a "massive slap in the face", arguing it was "pointless to have a manifesto commitment to stop oil and gas and then say, 'we're just going to approve the largest new fields'".

Estimates put Rosebank's lifetime emissions at up to 254m tonnes of CO2 equivalent, with production running to 2051 — a year beyond the UK's net zero deadline. Jackdaw's lifetime emissions are put at around 36m tonnes.

Khan also warned that the cross-party consensus on climate had collapsed, accusing opponents of veering "wildly between denialism and fatalism", while insisting progress remained possible. Downing Street has been approached for comment.