Owen Smith urges councils to take lead over mergers
Shadow Welsh Secretary Owen Smith has urged council leaders to "pick up the baton" and take the lead in reforming local government.
Mr Smith says councils should be trusted to drive any possible mergers.
In a report published in January, a Welsh government commission recommended the number of councils should be cut from 22 to 12 or fewer.
The issue will be high on the agenda when local government leaders meet for their annual conference this week.
The Williams Commission said public services could be delivered more efficiently by fewer councils and suggested a new local authority map for Wales.
'Get on with it'
Labour's Mr Smith said councils were aware of the need for reform, but insisted it had to be a collaborative process and "not something this imposed from above".
"It has to be driven by local government itself because that's the way in which we will end up with the best fit between local services and local people," he said.
"I'm saying to local government leaders: 'It's up to you, pick up the baton now and challenge yourselves to renew and refresh yourselves'."
The Labour MP for Pontypridd added: "They need to be trusted to get on with it, but they need to get on with it."
The proposed mergers included joining Ceredigion with Pembrokeshire and possibly Carmarthenshire.
But Ceredigion's Plaid Cymru council leader Ellen ap Gwynn told the BBC's Sunday Politics Wales programme there was no enthusiasm for mergers.
"There is no spare cash to fund any reorganisations. What we need to do is keep our focus firmly on the ball of service delivery," she said.
"That's what people on the ground want.
"Local people need local services and pulling the focus away from those services will not do anyone any good."
Councils are awaiting the Welsh government's formal response to the Williams Commission recommendations.
In a statement the Welsh government said: "An announcement on the Welsh government's preferred map of local authorities will be made before the summer recess, along with an update on how we are taking forward the Williams agenda."
It is an issue which will be high on the agenda of discussions at the Welsh Local Government Association's conference in Llandudno on Thursday.
First Minister Carwyn Jones said this week that some councils were incapable of improving education in their area, giving further urgency to the need to cut the number of councils from the current 22.
Welsh Conservative leader Andrew RT Davies said Labour were too focused on lines on a map, rather than deciding which functions councils should have and their funding.
He said: "The first minister needs to show leadership on this issue rather than dithering as he is at the moment."
Sunday Politics Wales, BBC One Wales, Sunday at 11:00 BST.