Plans to build a new "garden town" could be scrapped over concerns about a potential nuclear emergency.
The proposed 15,000-home development in Grazeley is within a couple of miles of nuclear weapons factory AWE Burghfield.
West Berkshire Council had to extend a "detailed emergency planning zone" (DEPZ) for the plant, taking in most of the site earmarked for homes.
That means anyone living in the zone could be affected by a "reasonably foreseeable" radiation emergency.
While there has been no change to the risk of an incident at AWE Burghfield, legislation required a review of the emergency planning which found the facility's DEPZ must cover a larger area, according to Shinfield Parish Council, which falls within the extended zone.
Three Berkshire councils that have worked jointly on the plans are now reviewing the project, according to the Local Democracy Reporting Service (LDRS).
West Berkshire Council has pulled out, while Wokingham Borough Council said it is looking at alternative sites because the Grazeley plan "may no longer be achievable".
Reading Borough Council said it has not pulled out but insisted the project "cannot be delivered at this time" without the support of the other two councils.
The Ministry of Defence has also objected to the proposed development, stating that the new homes should not be built within the DEPZ.
Wayne Smith, Wokingham council's planning lead, said: "This is a disappointment. We believed a garden town at Grazeley was a great way to provide homes local people need in a way that would safeguard our environmental and economic future.
"It seems that perhaps the Ministry of Defence isn't in step with other parts of the government, as they awarded Grazeley garden city status in 2019."
Last year, the government announced a £3.7m fund for the Grazeley development and four other "garden towns", which were expected to provide 64,000 homes across England, LDRS reported.
However, earlier this year, it rejected a bid for £250m to support the Grazeley project.
AMENDMENT: A previous version of this article stated the Office for Nuclear Regulation extended the DEPZ, however, it has been clarified that since May 2019 West Berkshire Council has responsibility for setting the zone's boundaries.