One of the most important West Midlands planning inquiries for years gets underway tomorrow as council leaders begin attempting to overturn proposals for up to 445,000 new homes to be built across the region by 2026.

A public hearing into the Regional Spatial Strategy is being held at Molineux football stadium in Wolverhampton and is expected to last for two months. The region’s 38 councils have joined together to oppose an attempt by the Government Office for the West Midlands to get approval for the biggest increase in housebuilding for decades.

The 445,000 target, set out for GOWM in a report by independent consultants Nathaniel Lichfield and Partners, is 80,000 more than the maximum number of new homes the councils believe can reasonably be delivered without building on green belt or greenfield land.

Ministers ordered GOWM to conduct its own research after becoming frustrated at the failure of councils to adopt higher housebuilding targets. The government has ordered authorities to do more to address the housing shortage, by developing on previously safeguarded land if necessary.

The councils, represented by the West Midlands Regional Assembly, point out that their preferred figure of 365,000 represents a 50 per cent increase on housing targets in the existing strategy and is at the upper end of what can reasonably be achieved.

Interested parties including housebuilders, engineers, environmental groups and business organisations will also give evidence at the hearing.

WMRA director of policy Mark Middleton, who will make the opening address, said the figure of 445,000 was “pie in the sky” and unlikely to be delivered, even if it was enshrined in the Regional Spatial Strategy.

Economic recession would make it impossible for councils to meet the target, he warned. Adopting such a figure would concentrate development on easy-to-sell greenfield land and would risk destroying the economic balance of the region by encouraging new build in the countryside and rural villages, while contributing to further decline in cities and towns.

Mr Middleton added: “The fear is that a dash for growth demanded by the government will, in fact, undermine the urban renaissance while putting more development pressure on rural areas.”

The inquiry, presided over by a planning inspector, will also decide how much land in the West Midlands should be zoned for employment, shops and offices. A decision on the targets is unlikely to be made by the government until next year.