The recession must not be used as an excuse to force the West Midlands into an unsustainable dash for housing growth, a senior planner will warn today.

Giving evidence at the opening session of a public inquiry into the Regional Spatial Strategy, Mark Middleton will say that opening the floodgates to a proposed 445,000 new homes across the region by 2026 would be a “short-term fix” that would put green belt at risk and add to the exodus of families from the Birmingham, Coventry and Black Country conurbation.

Mr Middleton, director of policy at the West Midlands Regional Assembly, believes the government’s attempt to force the region’s 38 councils to deliver the biggest growth in new housing for decades is likely to strike a fatal blow at the so-called urban renaissance – the regeneration of large towns and cities.

He will say: “It is the assembly’s firm submission that continued large-scale migration from the major urban areas will create social, environmental and economic harm to the region as a whole and the major urban areas in particular. The region’s previous overspill policies of the post-war era that sought to encourage and manage this process of out-migration are no longer fit for purpose and the Minister’s twice-confirmed Regional Spatial Strategy is the correct policy stance that we seek to update and continue.”

The two-month hearing, at Molineux football stadium in Wolverhampton, will focus largely on a clash between the regional assembly and the Government Office for the West Midlands over how many new homes should be built up to 2026. The regional assembly, representing the councils, believes 365,000 is the maximum figure achievable.

Mr Middleton will suggest “phasing and the managed release of land” is the appropriate response to changing economic circumstances with annual monitoring to ensure that appropriate house building targets are being met.

He will say: “Proposals by others for additional development will cite the need for flexibility, but it is the duty of a regional strategy to provide a consistent policy framework against which individual proposals can be measured for their cumulative impact.

“In the current economic situation, flexibility may be sought for alternative forms of development that can happen in the short term, regardless of longer-term needs.

“Economic recovery will, in particular, need a suitable supply of employment land and town centre commercial sites and these must not be lost in a rush for short-term development gain.”

The regional assembly’s warning will be echoed at the inquiry by the Campaign to Protect Rural England.

CPRE West Midlands spokesman Gerald Kells said developers would “cherry pick” green field sites at the expense of much-needed urban regeneration if large areas of the countryside were released for housing.

The rush to build in rural areas would make social polarisation worse, he added.