St Albans City and District Council last adopted a local plan in 1994. The authority was one of 15 threatened with central government intervention in 2017 over their failure to adopt an up-to-date development plan.
The council had submitted a local plan for examination in 2016 but it was knocked back by an inspector over its failure to comply with the legal duty to cooperate. St Albans later failed in its court challenge to overturn the inspector’s verdict.
The council submitted a revised plan for examination in spring last year.
In January, progress on the local plan was halted once more after planning inspectors cancelled examination hearings scheduled for next month, citing "serious concerns" about the document's "legal compliance and soundness".
Now, the inspectors, Louise Crosby and Elaine Worthington, have written a letter to the council's spatial planning manager Chris Briggs, saying that the west Hertfordshire authority has failed to engage "constructively and actively" with its neighbouring authorities on strategic matters.
These include the council's ability to accommodate St Alban's housing needs on non-green belt sites, and the proposed Radlett Strategic Rail Freight Interchange.
The report states that St Albans Council has not demonstrated that its approach to the green belt has been informed by discussions with neighbouring authorities about whether they could accommodate some of the identified need for development, in accordance with the National Planning Policy Framework.
The report acknowledges that St Albans Council published a joint updated duty to cooperate position statement with neighbouring Dacorum Council in January this year, which is expected to result in the publication of a draft statement of common ground in May.
But it says the failure to produce such statements so far demonstrates that the council has not complied with the duty to cooperate, meaning that the non-adoption of the plan must be recommended.
"We have not been persuaded that the duty to cooperate has been satisfactorily discharged by the council and if this is the case the failure cannot be rectified during the examination", says the letter.
The letter also outlines concerns that St Albans Council has provided "inadequate" evidence to support its contention that exceptional circumstances exist to alter the boundaries of the green belt.
The council's plan includes the strategic release of 525 hectares of land from the green belt in order to meet its proposed strategy to deliver an average of 913 homes per annum up to 2036.
Crosby and Worthington write that the plan's reliance on the strategic release of green belt has ruled out an important potential source of housing on small sites.
The report says: "In looking at green belt releases we have concerns about the narrow focus that has been placed on only strategic sites.
"This has ruled out a number of sites that have already been found to impact least on the purposes of the green belt. It may well also have ruled out other non-strategic sites with limited significant impacts on the green belt which may have arisen from a finer grained green belt review."
The letter adds that the inspectors will not reach "an absolute or final position" until the council has had a chance to consider and respond to the letter.
However, it adds: "In light of our serious concerns regarding the duty to cooperate, we consider it a very strong likelihood that there will be no other option other than that the plan is withdrawn from examination or we write a final report recommending its non-adoption because of a failure to meet the duty to cooperate."
Planning has approached St Albans Council for a comment but it had yet to respond at time of publication.