The current garden settlements programme was launched by the coalition government in April 2014 with the publication of the Locally-led Garden Cities prospectus.
The programme involves government financial support and advice for councils to deliver designated garden communities aimed at providing new housing, including garden cities, towns and villages.
A report by planning consultancy Lichfields published this week found that the overall garden communities programme includes aspirations for 403,000 homes in total.
This is across all existing 49 government-designated garden communities schemes.
However, of these, 119,000 (30 per cent) have no formal planning status - meaning they are not allocated in an emerging or adopted development plan or have any form of planning permission - while a further 143,000 (35 per cent) are included in emerging local plan allocations that are yet to be adopted.
The report warned that garden communities status is not a "golden ticket" to securing an allocation or planning permission, and that "a number of proposals have experienced delay because of insufficient evidence that the schemes are well conceived or deliverable over the plan period".
Of the homes in the programme with formal planning status, 14,000 (three per cent) have already been built, another 81,000 (20 per cent) have outline permission and 46,000 (11 per cent) have been allocated in local plans.
Lichfields estimated that, in the 24 local authority areas with garden community allocations in adopted plans, these allocations made up 30 per cent of the councils’ total housing requirements on average.
However, that proportion is up to two thirds in some areas, "where the ability to sustain a five-year housing land supply will be overwhelmingly dependent on successful implementation of the garden village," the report found.
In addition, the report estimated that around half of garden communities already had some adopted allocations or outline permissions at the time they were designated by the government.
"This suggests that in some cases, the designations are existing projects that have been ‘badged’ as garden communities and/or their place within the programme is intended to signal support for their delivery rather than to establish the principle of development," the report said.
Modelling undertaken by the consultancy suggested that the programme will take until at least 2050 to fully build out if there are no unforeseen delays.
It predicted that garden communities will only deliver around 21,000 homes over the next five years, before ramping up to a peak delivery rate of around 16,000 a year between 2030 and 2044.
Lichfields further found that only 22 out of the 49 designated garden communities are standalone settlements, while eight are major new settlements clearly linked to nearby towns, and the remaining 19 are urban extensions.
In total, the research found that garden settlements are set to provide around 600 hectares of employment land, providing just under 350,000 jobs.
In June, housing secretary James Brokenshire announced almost £3 million of government funding for an extra 19 garden villages across England, which he said have the potential to deliver 73,000 new homes.
The Ministry of Housing, Communities and Local Government was asked to respond to the report but declined to comment due to purdah restrictions.