Southend and Thurrock Councils have been warned they will be at risk of a legal challenge if they fail to integrate climate change plans within planning policy.

A group of lawyers from the environmental group ClimateEarth said Essex’s two unitary authorities are among 100 councils they plan to write to and ask how they will make carbon reduction targets central to their long-term housing strategies, known as local plans.

Southend Councillor Carole Mulroney, who oversees environment and planning, said the council is dedicated to meeting environmental targets but more support is needed from central Government.

She said: “At its September meeting the cabinet will be considering a motion to declare a climate change emergency which has all party support.

“This commits the council itself to achieve net zero carbon by 2030, if not earlier, and to work with the community and other agencies to achieve the same target borough-wide.

“Local plans work to a statutory cycle and the Southend Plan is in its early stages. We are well aware of the obligations which need to be taken into account in that process and already have an approved vision for all our work aimed at 2050. This includes climate change issues.

“All these efforts do not come easy or cheaply so we will be calling on Government to give all councils the necessary funding to reach the targets. You cannot keep cutting funding and expect the council to continue to provide all its services and also advance these very important commitments.”

Under Government guidelines, Southend's local plan will need to show how 24,000 new homes can be built over a 20-year period, along with infrastructure and job growth, while Thurrock Council will need to plan for almost 32,000 homes.

ClientEarth climate lawyer Sam Hunter Jones said: "So many of the daily decisions around new and existing infrastructure – such as new buildings, roads and utilities – are made at the local level. All of these decisions will ‘lock in’ an area’s future emissions and its resilience to climate change.

"Scientists warn that we have 10 years to transform our economies and avoid catastrophic climate change, but decisions that will have ramifications for decades are being made now by authorities with no idea if these decisions are consistent with national and international commitments to limit emissions.

"In July this year, the Committee on Climate Change criticised the UK’s continued failure to take action on emissions from buildings and transport – two sectors where local planning plays a critical role."

Thurrock Council was contacted for comment but did not respond