The duty to cooperate and why plans fail on it
Section 33A of the 2004 Act obliges authorities and prescribed bodies to engage constructively on strategic matters. Unlike soundness, a breach cannot be fixed by main modifications.
The duty to cooperate is a legal test applied to local plans, not to planning applications. Section 33A of the Planning and Compulsory Purchase Act 2004, inserted by section 110 of the Localism Act 2011, obliges local planning authorities, county councils and a list of prescribed bodies to engage constructively, actively and on an ongoing basis when they prepare a development plan document that deals with a strategic matter. The examining inspector checks it before anything else, because a plan that fails the duty cannot be saved.
That last point is the one that decides plan-making programmes. Soundness can be repaired mid-examination through main modifications. The duty cannot.
What section 33A actually requires
The duty applies to the preparation of development plan documents, and also to activities that prepare the way for them, which is why evidence base commissioning and early options work are fair game at examination. Three words carry the weight: constructive, active, ongoing. Constructive means the engagement had a purpose and produced something. Active means the authority initiated contact rather than waiting to be consulted. Ongoing means it did not stop when the regulation 18 consultation closed.
The prescribed bodies are set out in regulation 4 of the Town and Country Planning (Local Planning) (England) Regulations 2012. The list includes the Environment Agency, Historic England, Natural England, the Civil Aviation Authority, Homes England, relevant NHS bodies, the Office of Rail and Road, transport authorities and the Marine Management Organisation. Check the current text of regulation 4 rather than an old plan's compliance statement, because the list has been amended.
What the section does not require is agreement. An authority can engage properly, take a different view from its neighbour and still pass. Inspectors say so repeatedly in their preliminary questions.
The strategic matters that engage the duty
A strategic matter is defined in section 33A(4) as sustainable development or use of land that has or would have a significant impact on at least two planning areas, including in connection with infrastructure that is strategic and has or would have such an impact. In practice the recurring ones are housing numbers and their distribution, employment land, Gypsy and Traveller accommodation, strategic transport and highway capacity, waste and minerals, water supply and wastewater treatment, green belt review across a boundary, and habitats issues such as recreational disturbance or nutrient neutrality across a catchment.
Housing is where most examinations turn. Where an authority cannot meet the figure produced by the standard method for local housing need within its own boundary, the shortfall is a strategic matter by definition, and the authority has to show it asked its neighbours whether they could take it.
Asking late does not work. A letter sent after the regulation 19 publication version was settled tends to be read as a box-ticking exercise, because by then the plan's spatial strategy could not absorb a different answer.
The evidence an inspector expects to see
Authorities submit a duty to cooperate compliance statement with the plan. The useful ones are chronological and specific. They name the body, the date, the strategic matter, the position each party took and what changed as a result.
The strongest single piece of evidence is a signed statement of common ground on each strategic matter. A weak statement lists meeting dates and says the parties will continue to work together. A strong one says that authority A has a shortfall of a stated number of dwellings, that authority B has tested whether it can accommodate any of it, that B's answer is a stated number or none, and gives B's reasons.
Officer-level correspondence helps. Minutes of a joint strategic planning board help more, because they show a standing mechanism rather than an exchange of letters. Where a neighbour objects on the duty, the inspector will usually ask both authorities to explain the history at the hearing session.
Why a breach cannot be fixed
Section 20(5)(c) of the 2004 Act requires the inspector to consider whether the authority complied with any duty imposed by section 33A. Section 20(7C) then limits what the inspector can recommend. Where the duty has not been complied with, the recommendation is that the plan should not be adopted, and the modification power that rescues unsound plans is not available.
So the practical sequence is familiar. The inspector writes to the authority after the initial assessment, raising the duty. The authority looks at the correspondence trail, concludes it cannot demonstrate active engagement on the strategic matter, and withdraws the plan under section 22 rather than take the recommendation. Preparation then restarts, usually with a fresh call for sites.
The consultant fees are the smaller part of the cost. An authority without an up-to-date plan is deciding applications against policies that lose weight every year, and its five year housing land supply position is harder to defend.
Where unmet need actually goes
Nothing in section 33A makes a neighbouring authority take another area's housing. The duty makes the conversation compulsory and the record of it auditable. Redistribution happens through a joint plan, a spatial development strategy, a formal memorandum recorded in statements of common ground, or not at all.
Tightly bounded urban authorities with green belt on three sides produce the hardest cases. The honest position, and the one that survives examination, is usually that the authority asked, the neighbours declined for stated reasons, the shortfall is quantified and the plan explains how it will be revisited. An authority that quietly reduces its own need figure to make the arithmetic work is inviting a soundness challenge on top of the duty question.
The repeal that has not landed yet
Section 88 of the Levelling-up and Regeneration Act 2023 provides for the repeal of section 33A, with national policy expected to set an alignment requirement in its place. The provision has to be brought into force by regulations, and a policy that has been announced but is not yet in force changes nothing for a plan in preparation now. Verify on legislation.gov.uk whether it is in force at the point you advise. As at September 2026, section 33A still applies, and a compliance statement that assumes otherwise will not survive the inspector's first letter.
What this means when you are promoting a site
For anyone making representations, the duty is a live line of attack and a limited one. If the strategic matter that affects your site was never discussed with the authority next door, say so at regulation 19 with dates and documents, because raising it for the first time at the hearing looks opportunistic.
The flip side matters more often. A plan withdrawn on the duty leaves the authority determining applications under older policies, which changes the balance under section 38(6) of the 2004 Act and can make a site that was not allocated worth pursuing. Track the inspector's post-hearing letters rather than the council's press release.
PlanScope drafts the application-stage documents that follow, and you can browse the report types by category or enter a postcode on the home page to see which ones a site is likely to need. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. This is general guidance, not legal advice, so check the position with your local planning authority or a qualified professional before relying on it.
Frequently asked questions
Does the duty to cooperate apply to planning applications?
No. The duty to cooperate under section 33A of the Planning and Compulsory Purchase Act 2004 applies to the preparation of development plan documents and to activities that prepare the way for them. A case officer determining an application is not exercising it, although the outcome of a plan that failed the duty will affect how much weight the emerging policies carry.
Is the duty a duty to agree with neighbouring authorities?
No, and inspectors repeat that regularly. Section 33A requires engagement that is constructive, active and ongoing on strategic matters. Two authorities can end examination still disagreeing about how unmet housing need should be distributed, provided each can show it engaged properly, considered the other's position and recorded the outcome.
What happens if an inspector finds the duty was not met?
The inspector recommends that the plan is not adopted, and there is no route to fix it during that examination. Most authorities withdraw the plan before that recommendation is issued. Preparation restarts, which in practice costs a plan-making programme one to two years and leaves the authority exposed on housing land supply.
What is a statement of common ground for?
It records the strategic matters two or more authorities have discussed, the position each has reached, what has been agreed and what has not, and who signed it and when. It is the main written evidence of cooperation at examination. A statement that only lists meetings, with no agreed position on the strategic matter, carries little weight.
Has the duty to cooperate been abolished?
Section 88 of the Levelling-up and Regeneration Act 2023 provides for repeal and for a replacement alignment policy, but the provision has to be brought into force by regulations. Check on legislation.gov.uk whether it is yet in force before advising on it, because until section 33A is switched off it applies to every plan in preparation.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.