The policy, based on the latest advice, was due to come into force next month, but the minister said that was no longer "achievable".
Opposition parties and environmental campaigners have expressed concern at the delay.
The Welsh government said it was important to "get it right".
Ministers want to update the planning rules, known as TAN 15, to reflect the risk of flooding and ensure future development considers the potential impact of climate change.
The new policy will require developers and councils to consult maps produced by Natural Resources Wales (NRW) that show projected as well as current risk levels.
The government had intended to introduce the new rules on 1 December 2021, but a week beforehand they were postponed after councils raised concerns.
At the time, Minister for Climate Change Julie James said the delay was to "enable local planning authorities to consider fully the impact of climate change projections," and that the rules would come into force on 1 June 2023.
"There would be no further extension," she warned.
However last week, Ms James wrote to Senedd members (MSs) saying that date would "no longer be achievable," and it that it was "unlikely" the changes would happen "before the end of this year".
She said this was because the government was still considering responses to a new consultation carried out on revised proposals.
Speaking to the BBC's Politics Wales programme, the Welsh Conservatives' climate change spokeswoman Janet Finch-Saunders described the delay as "unacceptable".
Plaid Cymru MS Heledd Fychan said the postponement was "not helping those living at the continued risk of flooding".
"The planning system needs to be reformed, needs to be changed, this is a long time coming and should already be in place," she added.
Environmental campaigners have also expressed concern at the delay, with the chief scientist at Greenpeace UK Doug Parr telling the programme: "Every year, every month that we're installing things that need to be changed later is cost and difficulty.
"We know the misery that flooding can inflict upon people so we really urge the Welsh government to get this out as quickly as possible.
"Of course it's important that it's right, but there is no time for delay."
Responding to the comments, the minister for climate change told the programme the revised rules were designed to "make sure that climate adaptation is properly done in our local authorities, that the serious flood containment assessment plans are in place, and that we have the right development for our towns and city centres so that it's resilient into the 21st Century".
"That's not something you can do overnight and it's important we get it right," she said.
In the meantime councils have welcomed changes made to the wording of the proposed new rules since they were first due to be implemented.
Swansea Council leader, and Welsh Local Government Association spokesman, Rob Stewart, said the changes as they were initially put forward would have prevented the redevelopment of large swathes of Wales' major towns and cities.
However, the revised wording of the policy is "much, much better", and supports "sustainable development," he added.