The rule has been highlighted by last month's withdrawal of the development consent application for the 700MW Rampion wind farm off the town of Brighton in East Sussex on England's south coast.
Developer E.on submitted its application to build up to 185 turbines along with its environmental statement on 14 December to the UK Planning Inspectorate (PINS), which will decide the outcome. However, it withdrew the application on 2 January.
In a letter to PINS, E.on said it needed to extend the consultation to more local authorities deemed to be affected by planning legislation, including Surrey County Council and Sevenoaks District Council in the county of Kent, both of which border West Sussex, but are not on the coast.
E.on hopes to resubmit the application to build the wind farm this month, pending the outcome of the consultation.
Angus Walker, a partner at Bircham Dyson Bell, a law firm that advises on permitting matters, said: "If an offshore development is likely to have an onshore sub-station then the authority of that area is a host authority and needs to be consulted."
Widenening the net
The law extends to consulting authorities that share a boundary with host authorities - even if they do not want to be consulted. The planning department at Sevenoaks District Council said it did not know anything about the consultation. All such consultees must be given 28 days to respond to a development plan.
A spokeswoman for E.on said: "We want the application to be complete before PINS decides whether to accept it, and the only way to do this is to withdraw it and resubmit again as soon as we are ready.
"We remain completely committed to the project, but wish to take extra time now to maintain our comprehensive approach to consultation."
This latest delay to the project follows another minor hold-up last autumn, when a high level of public response to the Rampion plan prompted E.on to reschedule submitting its application.
In December, E.on announced it was reducing the number of turbines at the site after concerns raised by the consultation. This included a change to the project's layout following talks with surfing group Surfers against Sewage.
E.on's other offshore wind projects include the 630MW London Array 1 wind farm, Germany's 60MW Alpha Ventus and the 288MW Amrumbank West wind farm, planned for the German North Sea.