text: Nearly 25,000 signatures - 10% of Cardiff's voters - are needed to force a vote on the issue.
  But Labour councillor Ashley Govier told BBC Wales only about 8,000 have been collected.
  Cardiff council's Labour group said it was "willing to take the lead from public opinion on this issue".
  The Mayor for Cardiff campaign was launched earlier this year with a budget of more than Â£20,000.
  Daran Hill, from the campaign, said at the time that an elected mayor was a "new, fresh idea" that could "energise the people of Cardiff".
  There are currently 17 directly-elected mayors in England with more on the way, but there are none in Wales.
  Mr Govier, a councillor for Cardiff's Grangetown ward, said the debate has "moved on" and a regional mayor was now needed.
  "We're not going to hit the target, especially because the council refused to allow online petitions," he said.
  "We feel we've moved the debate on and the focus now needs to switch to a regional mayor for south east Wales. We have to go bigger."
  Mr Govier claimed the Cardiff Capital Region City Deal - a funding package agreed between UK, Welsh and local government worth Â£1.2bn over 20 years - was beginning to stall "because of governance".
  "The region has to work together on infrastructure and transport," he said. "A regional mayor is needed."
  He added there are "sympathetic ears throughout the region and across political parties".
  Ceredigion is the only Welsh local authority to have had a referendum on the matter. Voters there rejected the idea in 2004 by a margin of nearly three to one.
  A spokeswoman for Cardiff council's Labour group said: "Cardiff Labour are willing to take the lead from public opinion on this issue, and as we have seen there is very little interest in introducing a further level of bureaucracy.
  "The City Deal is definitely not stalling and is moving forward, despite uncertainty caused by Brexit.
  "It will be a huge boost for Cardiff and the region, and suggestions to the contrary are just mischief making."
  A Wales Office spokesman said: "The Cardiff City Deal is the biggest of its kind in the UK and we are confident this ambitious project is on target."
  The Welsh Government declined to comment in response to Mr Govier's comments.
target: An attempt to trigger a referendum on Cardiff having an elected mayor is going to fail, a campaigner has admitted.