The proposal for a ferry service between Whanganui and Motueka will not be included in the Whanganui port revitalisation business case presented to government in June.
Midwest Ferries - who plan to operate the service - presented a feasibility study to Whanganui District Council in May which suggested a single-ferry freight service was both technically and commercially feasible.
But a peer review commissioned by Whanganui District Council said the study contained "an unusually large number of areas 'parked' for future study and some critical assumptions".
The review by Murray King & Francis Small Consultancy and Ian Wallis Associates also raised concerns about resource consenting which it said the original report "was virtually silent on".
"We feel that the consenting process could involve significant effort, time, cost and potentially be a serious obstacle to the project," it said.
"At the very least a feasibility study should have noted it in more detail and pointed out the risks, especially as the works and operations are in sensitive areas."
Whanganui mayor Hamish McDouall said the review was commissioned to help the council and the community understand the feasibility and impacts of a large ship operation from the Whanganui Port.
"This does not prevent a ferry service from operating in the future, if it meets the requirements to operate within the particular physical make up of our river port, is economically viable and practically feasible," he said.
Midwest project director Nik Zangouropoulos, who co-authored the original feasibility study, said he had "no major objections" to the peer review.
He said the original feasibility study was constrained by time and was only intended to get the proposal to the stage where a detailed business case could be commissioned.
"Broadly speaking we agree there are significant gaps that need to be filled and we intend that to occur in the next stage."
Mr Zangouropoulos was not disappointed the ferry proposal was not part of the port revitalisation business case at this stage.
"We fit into the medium to longer term vision," he said.
"The most important thing for us is that it is recognised as a possibility. We now need to prove that what we've got proposed is genuinely viable."
The peer review said while there may be a profitable market for Midwest's proposal it had not yet been sufficiently made.
"A significant number of gaps need to be filled before a developer would proceed and some of them need filling before the funders are likely to assist with the next stage."
The council has commissioned two further reports which address the port from an operational and environmental perspective and explore the use of the port by large vessels.
Tasman District Council will make its decision about the viability of a feasibility study for a ferry service at the Motueka Port at its Council meeting on June 22.