An independent inspector chairing a public hearing into viability of a huge waste plan for north London says councils must prove they have properly consulted.

Planning Inspector Andrew Mead says seven councils who want permission for the North London Waste Strategy – which includes proposals to use land at Pinkham Way, New Southgate – to be granted must prove they have consulted with other authorities impacted by the plan.

Mr Mead said the seven councils had a “duty to cooperate” with authorities in the east and south-east of England who receive waste from north London, and have complained to the public hearing about the impact of the plan.

The move throws into doubt the future of the 15-year plan, which includes the huge Pinkham Way facility that would deal with about 300,000 tonnes of waste a year on the land off the A406.

The seven boroughs – Barnet, Camden, Enfield, Hackney, Haringey, Islington and Waltham Forest – say that they have “engaged constructively” with the authorities objecting to the plan, and argue they have cooperated with all the bodies they need to legally for the plan to proceed.

The six-day public hearing to address the multi-million pound strategy was adjourned indefinitely after just two hours earlier this month because of the objections from the South East Waste Planning Advisory Group and the East of England Waste Technical Advisory Body.

Campaigners have staged protests during the last 18 months outside council meetings across north London calling for any plan for a plant at Pinkham Way to be abandoned, due to concerns over air quality and fleets of waste trucks that could bring heavy traffic to the already congested North Circular Road.

The seven councils must now wait for up to a week to see if Mr Mead accepts their arguments and have a right of appeal if he rules against them.