Big city mayors will help to cut unemployment and improve public transport – but they must be given more powers, a major study has recommended.

The hard-hitting report is published by a think-tank led by former Government Minister Lord Adonis, who earlier this year delivering a highly critical speech blasting Birmingham as a city with weak leadership and a bleak future.

Lord Adonis, a former transport secretary, angered city councillors by claiming Birmingham had “made a big mistake” in refusing to have a powerful city mayor like Boris Johnson in London, when he delivered the annual speech of Birmingham’s Lunar Society in March.

The report, published by Lord Adonis’ think-tank the Institute for Government, backs the Government’s plan to hold referendums on creating elected mayors in England’s largest cities, including Birmingham and Coventry.

But it argues that mayors should have more powers than the Government is proposing, including the power to give planning permission to major projects.

The mayor should chair the transport authority, the report says.

And he or she should also co-chair the local enterprise partnership, which supports industry, alongside a senior figure from the business community.

The study also resurrects the idea of a “Greater Birmingham” or “West Midlands” Mayor who would represent an area larger than the city.

This would be called a “metro mayor”, according to the study.

It states: “We recommend that metro mayors have the same powers to those identified for local authority mayors but over a wider area.”

Lord Adonis said: “Evidence from the UK and abroad shows that elected mayors can have a transformative effect on city economies.

“But if they are going to succeed, government first has to give them the powers to make a difference.”

The report does not specify which areas a “metro mayor” would cover, but in Birmingham’s case a mayor might be responsible for neighbouring areas such as Solihull, Dudley, Walsall and Sandwell as well as the city.