Birmingham's housing shortfall has been underestimated by 5,000 – despite plans to build in the green belt - new documents reveal.
Spiralling demand for new housing has seen the city's overall requirement rise to 89,000, compared to the 84,000 predicted.
However, the city can only find space to build 51,100 - meaning the shortfall is creeping close to 38,000.
Rising demand comes as the city's population is expected to soar by 150,000 - equivalent to the population of Oxford - over next 16 years.
Against a backdrop of talks over a combined authority, uniting Birmingham with six other authorities in the region, the council will have to work with others to address the shortage.
Birmingham City Council's director of planning and regeneration, Waheed Nazir, said co-operation across the West Midlands was vital to addressing the issue.
He said: "Clearly, Birmingham can't meet its housing requirement and as a consequence we are going to have to work together closely, moving forward.
"Combined authority or no combined authority, there is already a duty to co-operate. We have to work together as neighbours. But a combined authority would bring greater cohesion to the issue of dealing with the housing requirements of the region.
"Some areas will want more housing and some less, but between us we can agree a strategy – that is the strength of a combined authority."
The rise in housing demand is revealed in the Birmingham Development Plan, which goes before the city council's cabinet on July 27.
It seeks to map out how the city will grow, with about 100,000 jobs expected to be created by 2031.
The plan seeks to stimulate £9 billion of investment from property developers in 40 major brownfield sites.
Central to the plans in Birmingham are proposals for residential development at Langley, in the Sutton Coldfield green belt.
Meanwhile, a levy aimed at encouraging development within the city while contributing to the cost of related infrastructure is set to be adopted by the city council.
The Community Infrastructure Levy (CIL) ensures certain types of development contribute towards the infrastructure needed to support growth in the city, as set out in the Birmingham Development Plan. This could include schools, health and community services, improvements to open space, better transport and highways improvements.
Consultation has already taken place on the proposed charges which were then subject to examination hearing before an independent planning inspector.
The charges will be set at a level which will secure essential funding while not prohibiting investment in the city.
Councillor Tahir Ali, cabinet member for development, transport and the economy, said: "These CIL charges are a direct result of engagement with the private development sector.
"Throughout the consultation process, we listened to their views and revised our charges to ensure that we strike the right balance between funding necessary infrastructure and the potential impact on the economic viability of development.
"These charges will still support growth and investment and will allow us to develop the infrastructure needed to support that growth and improve the well-being of local people.
"Birmingham City Council is one of the few local authorities that have been given the go-ahead to implement the new procedures in advance of an adopted development plan - a testament to the quality of the emerging Birmingham Development Plan."
Mr Nazir added: "CIL is a useful tool to enable us to deliver the essential infrastructure to facilitate our planned growth. We will keep the charges under constant review to ensure they remain reasonable and will continue to work closely with our development sector colleagues."
Government legislation means that Section 106 contributions from developers now have to be site-specific but CIL contributions will go towards a range of infrastructure projects across the city.