'Complex' devolution limits services, says Carwyn Jones
The devolution settlement for Wales makes it harder to improve services such as health and education, First Minister Carwyn Jones has said.
Setting out plans to restructure local councils, he said the devolution settlement was "cautious and complex".
The cross-party Williams Commission suggested roughly halving the number of Welsh councils from the current 22.
The Welsh Labour Party is consulting on a new map of 12 councils and is due to report back in September.
In the introduction to the Welsh government's formal response to the report, Mr Jones wrote: "We have been limited by a cautious and complex devolution settlement, an unfair funding framework and a set of outdated public sector structures designed pre-devolution.
"These deficiencies are not technical points. They constrain our ability to improve services, and to support the economy and well-being of people in Wales."
Speaking later he added: "Local authority mergers will protect and improve local services.
"They will help improve capacity of organisations to respond to the growing challenges they face.
"There have been too many interventions in recent years, where we have had to step in and take firm action in order to safeguard public services, particularly in some smaller local authorities. This cannot continue."
The Welsh government also published proposed legislation paving the way for councils to merge voluntarily if they wish.
Shadow Local Government Minister Mark Isherwood warned council bills should not "rise even further to pay for bureaucratic changes" and insisted it would be "irresponsible to push ahead when the cost of these changes will further hit service delivery".
"As we move forward - I sincerely hope Labour's first minister will put excellence in frontline services at the very top of the agenda, recognising that 'big' is not always beautiful, more efficient or cost effective," he said.
Plaid Cymru AM Rhodri Glyn Thomas said voluntary mergers would be a "piecemeal approach, rather than the full scale reform of public services that we need".
He said his party would have a "comprehensive policy" in its 2016 assembly election manifesto "on how different services can best be delivered".
Earlier, a member of the Williams Commission said people were being "let down" by poor public services.
Nick Bennett, soon to become Wales' public services ombudsman, said he was "disappointed" a cross-party deal could not be reached by Easter - the date set in the commission's report for ministers and councils to agree a way forward - and urged politicians not to treat the report's recommendations as a "political football".
"Too often services are poor and patchy. Perhaps you can have excellence and mediocrity or even failure within the same local government structure," he said.
"We've got to be more ambitious as a nation and we've got to insist upon better."