Earlier this year council leaders were optimistic of securing a deal by the autumn, after agreeing on proposals to establish a combined-authority.

But the Treasury now looks to have ruled this possibility out, after revealing its “priority” will be areas with directly elected mayors.

Speaking to the Herald, Treasury minister David Gauke claimed this model provides local authorities with “maximal” opportunities for devolved powers.

“To get the most powers you need the best accountability and that’s delivered by directly-elected mayors,” he said.

“We think [it’s] the best model… so we continue to encourage local authorities to go down that route.

“Those areas that don’t want to go down that route, we will of course still look at the devolution options there.

“I think the priority is delivering the directly elected mayor model.”

This renewed focus on mayors appears to contradict messages from the Department for Communities and Local Government, which has previously indicated support for a combined authority model.

Earlier this year, councils in Devon and Somerset voted in favour of creating a combined authority for the region, on the understanding this would improve the area’s chances of a devolution deal.

Critics of the mayoral model express concern about the ability of a single leader to effectively represent areas as economically and geographically diverse as Plymouth and the Mendips.

Responding to Mr Gauke’s comments, leader of Somerset County Council, John Osman, said his understanding “is that the Prime Minister does not think a mayor is essential for devolution”.

“Some initial public engagement this summer suggests that is a view shared by Somerset residents,” he added.

“We have a compelling case for devolved powers and budgets which has the potential to drive productivity, address challenges and capitalise on our many opportunities.

“We aim to continue these with the new relevant minister, Sajid Javid, in the near future to maintain the momentum and take our plans forward.”

Conservative MP for Wells, James Heappey, acknowledged that the recent change in Government leadership has resulted in changes to devolution policy.

He suggested this could provide the region with an opportunity to “take [its] foot off the accelerator” and review its proposals.

“If there is value in doing it, if it’s going to allow public services to be more efficient…. Then clearly we should go ahead [with a combined authority bid],” he said.

“[But] it makes no sense to change things just for the sake of changing things.”

Kevin Foster, the MP for Torbay – which recently voted to scrap its mayoral system – said many residents “won’t be itching” to have another elected mayor.

But he suggested the option is worth considering if it means “getting transport powers and an ability to deliver for local people”.

Mr Gauke did stress that the Government is still keen to extend devolution beyond the high profile city regions.

He said “a lot of focus has been on cities” but it would be good to “show how devolution can work in all parts of the country”.