Crumbling sea defences will get a £1.6m cash boost from the Welsh Government, but an assembly member says it is not enough.
A stretch of Old Colwyn promenade was described as "failing" in an earlier report for Conwy council.
Clwyd West AM Darren Millar said the cash "falls well short" but was "welcome nonetheless".
The Welsh Government said the scheme "will improve active travel facilities as well as coastal defence".
The estimated cost of repairing the defences from Porth Eirias to Cliff Gardens ranges from £2m to fix about 400m of wall to £36m for a full set of works on the whole 1.2km stretch, the Local Democracy Reporting Service said.
Mr Millar said the funds were not enough to meet "the overall total needed for a significant upgrade to the sea defences in Old Colwyn".
The defences along the promenade "play a vital role in protecting the main sewerage network, the A55 trunk road and then north Wales railway line", he added.
"They [the defences] have been in a very delicate state for over a decade and we've been warned time and time again by engineers that they are at risk of catastrophic failure at any time," he added.
"Work needs to start as soon as possible to ensure that Old Colwyn is no longer at risk."
The Welsh Government said it recognised "the importance of robust sea defences at Old Colwyn Bay which are key to protecting infrastructure and utility networks".
It added that in this assembly term it would invest £350m in flood and coastal risk management programmes "with funding prioritised according to risk to life and towards the communities most at risk".
The £1.6m invested in the promenade is part of a £14.5m investment in active travel schemes across Wales, it said.