Green campaigners on Monday launched legal action against the UK government after it authorised oil and gas production in the country's largest undeveloped field.

Uplift and Greenpeace said in a joint statement they were mounting separate legal challenges to prevent development of the Rosebank field in the North Sea off the coast of Scotland.

Britain's Conservative government led by Prime Minister Rishi Sunak in September approved the multi-billion-dollar project operated by Norwegian energy producer Equinor and Ithaca Energy, a subsidiary of Israeli group Delek.

Uplift and Greenpeace on Monday said they had applied to the Court of Session in Edinburgh for a judicial review of the decision.

It comes after almost 200 countries, including the UK, agreed last week that the world should be "transitioning away from fossil fuels" to achieve net-zero emissions by 2050.

"If Rosebank goes ahead, the UK will blow its own plans to stay within safe climate limits," said Uplift executive director Tessa Khan.

"It's that simple. If the government disagrees, it needs to provide evidence and prove it in court.

"The (UK oil and gas) regulator also needs to be open about its reasons for approving a huge oil field when we're facing a worsening climate crisis," she added.

The government said it would "robustly defend" itself against the legal challenges.

"The UK is a world leader in reaching net zero ... (but) we will still need oil and gas as part of our energy mix," a government spokesperson said.

The UK government maintains it must beef up energy security via continued production of fossil fuels following the invasion of Ukraine by key producer Russia, even if it means pushing back its target on net zero carbon emissions.