A consultants’ study ordered by the Government suggests that sufficient land can be identified in the West Midlands to build 445,000 new homes over the next 18 years – a quarter more than the maximum amount proposed by local councils.

The Nathaniel Lichfield and Partners report, which proposes substantial housing growth in Birmingham, Warwickshire, Worcestershire and Solihull, admits that green belt land will have to be sacrificed, but rejects fears that new-build in the countryside will lead to further population drift from cities to rural towns and villages.

The findings will come as a major blow to the West Midlands Regional Assembly which has submitted proposals to the Government for no more than 365,600 new homes to be built between 2006 and 2026.

A spokesman for the regional assembly said the study, demanded by the Government Office for the West Midlands after the assembly published its preferred housing figures earlier this year, was an “unprecedented” turn of events.

Policy director Mark Middleton warned that additional housing development in rural areas would not help Birmingham and the Black Country which had been fighting against a trend of migration to the countryside since the end of the Second World War.

And assembly chairman David Smith added: “It remains to be seen whether the Government will accept the view of London-based consultants or trust the collective wisdom and expertise of the 38 local authorities that underpins the strategy submitted by the assembly.”

Proposals from the Nathaniel Lichfield report will be submitted to a public inquiry into the Regional Spatial Strategy which is due to start in April. A planning inspector will make final recommendations to the Government about housing targets.

The survey sets out three options ranging from 51,500 more housing units than proposed by the assembly to 80,000 more units.

At the top end of new-build proposals, development in areas covered by Warwick and Stratford-on-Avon district councils would be almost twice that envisaged by the assembly – a total of 30,900 new dwellings.

Bromsgrove would see its share of new-build rise to 9,600 homes, South Worcestershire to 30,000, Solihull to 17,600 and Birmingham to 60,600. While green belt land would be required, the report makes it clear that councils would also have opportunities to review existing arrangements and extend green belt boundaries in some instances.

The report rejects fears that the economic downturn could leave thousands of new houses empty. It says an economic recovery in three or four years will see house prices rise again, making the existing housing shortage even worse.

Nathaniel Lichfield director Matthew Spry said migration from cities to rural areas would continue in any case and the number of new dwellings to be built would make no difference to the trend.

Dave Marr, head of housing and planning at the Government Office for the West Midlands, said the assembly’s proposal for 365,000 new homes “undershot the Government target by some way”.

Mr Marr added: “This is not an alternative strategy. It’s not a strategy at all. It looks at a number of different ways in which additional homes might be delivered in parts of the region.”

Mr Marr said GOWM would look carefully at the three options put forward before deciding which one to back at the public inquiry.