A City For All Londoners, published by London mayor Sadiq Khan in October, is the first step towards the creation of a new London Plan, the capital's over-arching spatial planning document.
In the document, the mayor pledges to "protect the green belt and other designated spaces" and to take "bold measures to meet as much of the city’s growth demands within London".
The mayor says that while he wants "to contain most growth within London", he also wants to work with local authorities in the wider South East to deliver "joint infrastructure investment corridors" that would open up development opportunities "beyond London’s borders".
In response to the consultation on A City For All Londoners, which closed earlier this month, local authority umbrella group South East England Councils (SEEC) wrote a letter to Khan outlining key concerns about the proposals.
The letter states: "We welcome your commitment to ‘accommodate as much of this (housing and employment need) growth as possible within London’, but understand there may still be a gap between housing demand and supply.
"We ask you to set out clearly how you will fully explore all options for tackling the challenge of meeting London's housing needs within London itself.
"To ensure a level playing field we ask you to consider green belt release to help meet your housing needs (like councils outside London have to) before exploring options beyond London’s boundary."
SEEC goes on to emphasise that "the mayor must not assume the South East has capacity to meet London’s additional unmet needs on top of [its own] existing high levels of growth".
It asks the mayor to outline "the benefits to South East councils of taking extra housing growth from London", such as accompanying infrastructure investment.
SEEC also calls for the mayor to "work pro-actively with councils in the South East on the implications of London’s growth and development".
According to A City For All Londoners, there is a "need to identify land in the capital to build at least 50,000 homes every year between now and 2041" to accommodate its fast-growing population.
A spokesperson for the mayor of London said: "The mayor has been working with councils in London and across the South East of England on a range of issues, including development policy and infrastructure investment.
"The mayor has no jurisdiction over house-building outside the capital and he has never asked any local authority in the South East to help meet London’s housing need, as he firmly believes that London is able to meet its population demands within its own boundaries and without building on the capital’s green belt.
"The mayor is informing and consulting the wider South East over his plans for London to ensure that coordinated, strategic planning takes place and that the entire region is better able to meet the unprecedented demand for housing."
The SEEC letter can be read here.