The nine RIEPs, which went live in April, were given a kick-start with a£185m three-year funding package from the Department for Communities & Local Government , ending in 2011.
But further funding is not expected to be offered, putting pressure on councils to come up with cash to secure the viability of the central pillar of the local efficiency agenda.
RIEPs replaced regional improvement partnerships and centres of excellence. In addition to councils, they include other local public sector bodies and aim to help deliver efficiency and improvement targets and share best practice.
Local Government Association policy consultant Clarissa Corbisiero said: "The noises coming out of the [DCLG] suggest that the package was a one-off and there will not be any more money available after that, but they have not said anything official yet."
Julian Morley, director of the South West RIEP, said he expected councils to subsidise their RIEPs in future.
"It will be more difficult to get funding for the next spending review and the onus is on RIEPs to prove that they add value. This is not just because of the current financial crisis, although that may have exacerbated the situation," he said.
The RIEPs have been in place for five months and leaders are set to meet local government minister John Healey later this month for a progress evaluation.
Keith Beaumont, Improvement & Development Agency programme officer, said that progress so far was good, with all the RIEPs starting to implement their delivery plans.