New mayors to be elected in the biggest cities must give England's regions a say in Brexit talks, a think tank said today.
Metro mayors in cities including Liverpool, Birmingham and Manchester, will get new devolved powers when they are elected next month, representing almost 10 million people and economies worth £214 billion, more than Scotland and Wales combined.
The New Leaders report, by the Institute of Public Policy Research (IPPR) North, claims England's cities could rival places like Frankfurt and Barcelona post-Brexit, using new mayoral powers.
The report looks at the powers new mayors will have and how they can use them to transform their city-regions, especially to make daily commutes "quicker, cheaper and greener".
But the think-tank warns these mayors must be given a voice alongside London, Scotland and Wales during Brexit talks, to make sure the rest of England is not forgotten.
While Scotland, Wales and Northern Ireland have been promised a "hotline" to Brexit secretary David Davis, the role of England's mayors remains unclear, the IPPR North report said.
Luke Raikes, report author and senior research fellow at IPPR North, said: "Next month, we'll see a real shift as Metro mayors take power, elected to lead city-regions across England and governing almost 10 million people.
"New Metro mayors must speak for England and the 'left behind'. They must not in turn be 'left behind' Scotland, Wales and Northern Ireland in Brexit talks.
"These mayors will be more than just figureheads.
"If they work with other local leaders, they can deliver real change.
"They could have an impact on the daily lives of their citizens: helping to solve the housing crisis, creating jobs and making public transport quicker, cheaper and greener.
"This could be the beginning of a devolution decade: if these mayors speak as one, and team up with the mayor of London, we could see local areas really taking back control from Westminster."
On May 4, voters in six English "city-regions" will head to the polls to elect new Metro mayors with transport, housing and job creation powers.
The regions are Greater Manchester, Merseyside, Cambridgeshire and Peterborough, Tees Valley, West Midlands and West of England.