Plymouth City Council has supported the creation of a large new local authority run by an elected mayor covering the whole of Devon and Cornwall, saying “we are stronger together”.

Council leader Tudor Evans (Lab, Ham) said the city must seize the opportunity presented by the government’s proposals for local government organisation to bring more powers and funding to the region.

Councillors also supported expanding Plymouth’s boundaries so it can remain a unitary authority sitting under a larger peninsula body which could result in a push to take over parts of the South Hams, although the boundaries have not been specified.

The government wants to scrap district councils, of which Devon has eight, in favour of authorities covering areas of 500,000 people. Plymouth became a unitary authority, meaning it is responsible for all local services, in 1998 but with a population of 274,300, it falls short of that.

The new town of Sherford, which sits in the South Hams district, is expected to have 12,000 residents when complete, and a number of other large developments in the South Hams are planned close to Plymouth.

The government’s deadline for responses to its proposals for devolution have to be submitted today, Friday.

Cllr Evans said Plymouth has to present “a powerful case” for its own existence, resisting any threat to putting it “out of business” and being subsumed into a more rural authority.

And he said by having one voice for the South West Peninsula, Plymouth would have a seat at the “grown ups table” and no longer be fighting over funds.

A large strategic authority of 1.8 million people would put the area on a par with the East Midlands, Manchester and Liverpool,” he said.

“For the first time we can act as one; a once-in-two-generations opportunity for regeneration and renewal.”

He said the status quo is not as option. “We need to get our hands on the reins that too many people in Westminster have held over us. We must not let devolution happen to us, we must make the rules and the waves.”

Conservative group leader Cllr Andy Lugger (Con, Southway) supported Cllr Evans’ motion for a strategic authority for the South West Peninsula and an extension to Plymouth’s boundaries, but said with the short time scale from the government, the public had been denied consultation.

He said devolution plans should go beyond party politics and be the catalyst to revive democracy.

Cllr Patrick Nicholson (Ind, Plympton St Mary) supported trying to bring power from London and the south east to the rest of the country.

Major issues such as the road and rail network, communications and aviation are issues that Devon and Cornwall needs to tackle together, he said, and the naval base and Derriford Hospital are as important to Cornwall residents as people in Devon.

Green councillor for Plympton Chaddlewood Lauren McLay said genuine devolution is a good thing to help local transport, housing, economic development and the environment, but she had doubts that Labour would listen.

She said Labour locally had ignored the public by disregarding their views in a public survey on changing the election process, and on a national level she said the two-child benefit limit [introduced by the Conservatives] had “pushed 10,000 children into poverty”.

Cllr Steve Ricketts (Ind, Drake) did not want to have a system with an elected mayor, concerns echoed by Cllr Lee Finn (Con, Budshead) who said the mayor would have the power to block decisions by councils. Cllr Finn also questioned who was going to pay for the £43 billion of debt that the country’s councils had racked up.

But Cllr Sarah Allen (Lab, Peverell) said the government’s proposals presented a chance to work together rather than “fighting for crumbs from Westminster”.

“Together we are stronger and this is a real opportunity for the South West to finally shine.”

The council voted by 38 votes to one to accept the motion for a new Devon and Cornwall authority, with four abstentions.