The battle for Sutton Coldfield's green belt looks set to dominate a four-week public inquiry into Birmingham's 17-year development plan.

Early exchanges in the inquiry at Aston University revolved around the council's proposals to release green belt land east of Walmley for the construction of a major factory and up to 6,000 homes.

On one side campaigners, including the Campaign for the Protection of Rural England, are arguing that any development is going too far, but on the other lawyers acting on behalf of a consortium of major housing developers and landowners claim Birmingham needs to go further and release more green belt land for construction.

The draft plan states that 84,000 new homes are needed between now and 2031 to meet demand caused by population growth and housing shortages.

Until now the council has argued there is only space for 43,000 more homes within the current urban area - although this number has now been raised to 51,000 following further analysis.

Last year the council planning department looked at and rejected the idea of releasing three further parcels of green belt land near Four Oaks – choosing just the site next to the A38 now known as the Langley Sustainable Urban Extension (SUE).

The Consortium of West Midlands Developers and Landowners has argued that the plan underestimates the housing demand and that space is needed for at least 112,000 properties.

In a statement to the inquiry Savills, representing developers, said: "In recognition of the sustainable location of the Langley SUE, and limited number of constraints associated with the Langley SUE area, any further release of land in the green belt in Birmingham's administrative boundary to the north of the Langley SUE should be in addition to, rather than instead of, the Langley SUE."

This is set to be the subject of detailed examination on October 28 - and Sutton Coldfield Conservative MP Andrew Mitchell is among those scheduled to speak in opposition to green belt development.

Sutton councillor Ewan Mackey, who is also opposed, said: "Every argument and discussion has so far come back to the green belt.

"The council's planning department is up against some very experienced counsel working for the developers and landowners.

"I would have thought it would be easier to defend a line that it would be ridiculous to build on the green belt at all. By giving away part of the green belt the council is making it easier for developers to argue there should be more."

He said that there is also hostility from neighbouring authorities, including the Black Country councils, to Birmingham's request that they accommodate a proportion of the new housing required.

The Black Country authorities argue that Birmingham has not adequately set out its case for requiring the release of land over the boundary.

Meanwhile, the row over the green belt has prompted Sutton Coldfield's only Labour councillor Rob Pocock to resign from the board of the much-respected Sutton Coldfield Charitable Trust.

Coun Pocock (Lab Sutton Vesey), who also opposes green belt development, claims the trust is pushing for further green belt land to be released to further its interests as a land owner.

He said: "Ever since the city council put a cap on the Sutton green belt development limiting growth to 5,000 houses by 2031, it has been bombarded by a blitz of objections from predatory land speculators who want the total jacked back up to 12,000 or more.

"It is a shame that the Sutton Coldfield Charitable Trust has got itself tangled up in this game, because it helps a lot of good causes in our area."

The trust would not comment on the issue but via its agent RPS, in a submission to the inquiry, it has argued that the further parcels of green belt land be released for development.