Two Welsh cities have joined calls for a cross-border economic “powerhouse” encompassing south-east Wales and the west of England.
Cardiff, Newport and Bristol councils want to form a regional powerhouse to boost economic growth.
A report says a “Great Western Powerhouse” could boost industry and improve transport links.
The two regions have “huge complementary strengths”, according to Cardiff council leader Huw Thomas.
The Northern Powerhouse is a strategy which featured a range of measures aimed at boosting the economy beyond the south-east of England.
It focused on improving transport links, boosting investment and devolving powers to elected mayors.
The report into the Great Western Powerhouse, commissioned by the three councils, said the UK economy “is being reshaped by devolution and the emergence of regional powerhouses”.
“But, there is a missing piece of the jigsaw in the west of Britain, along the M4,” it continued.
The report suggests a powerhouse could stretch from Swansea in the west to Swindon and Bath in the east, and as far north as Tewkesbury.
There are already three established city regions and plans for a new one, the report says, but no overarching powerhouse concept for the region.
The report argues that the Northern Powerhouse and another cluster, the Midlands Engine, “have been successful at attracting significant levels of government funding and investment”.
Mr Thomas used the cyber security and aerospace industries as examples of areas of “huge complementary strengths”.
“Between Cardiff and Bristol you’ve got the biggest creative hub outside London. So let’s build on those strengths,” he added.
The proposal calls for the UK and Welsh governments to help set up a cross-border organisation to co-ordinate the initiative.
The Labour mayor for the City of Bristol, Marvin Rees, said Bristol, Cardiff and Newport “have worked together for some years”.
“But, outside local government, normal people work across this border, people move between Bristol and Cardiff all the time,” he added.
“This is about us catching up with the way people are living.”
The report says the powerhouse would need to decide on its brand, although it suggests “Great Western Powerhouse” could be its name.
It calls for an integrated plan for road and rail improvements and an overarching industrial strategy to attract new and developing industries.
“We need to recognise the natural economic flow is east to west,” said Welsh Secretary Alun Cairns.
In a statement, the Welsh Government said it supports “vitally important” collaboration in the region “on the basis of respect for devolution and the different mandates of partners”.
Watch Sunday Politics Wales at 1100 BST BBC One Wales, or view on the iPlayer following broadcast.