Andy Meader, director of consultancy Pegasus Group, said that recent case law had established that the intensity of housing need was a key factor in demonstrating the exceptional circumstances required to justify green belt release in local plans.
"In other words, the greater the shortage of housing, the more exceptional the circumstances are likely to be," Meader said.
"If the objectively-assessed need is suddenly to reduce for any reason, then that can have implications."
"It is a very significant consideration," Meader said, which could have "a fundamental impact" on councils' ability to demonstrate exceptional circumstances.
Other key factors needed to demonstrate exceptional circumstances, he said, included fully investigating alternative sources of development in the area.
"It’s going to be very important to have undertaken those exercises," he said. "Otherwise, there is the potential criticism that you just don’t really know what potential there is."
Meader, whose firm has recently carried out a green belt review for Guildford Borough Council, added that authorities wanting to make green belt releases should justify such changes both in principle and on an individual site basis in order to demonstrate exceptional circumstances.
Mark Andrews, planning and housing policy manager at Coventry City Council - whose recently-adopted local plan released green belt land for 7,000 homes - said that key tips for carrying out a green belt review included having a clear and consistent methodology and working with a wide range of stakeholders.
He also advised that those undertaking reviews should have realistic expectations.
"Your review will never be accepted by everyone and it will never be perfect," Andrews said. "If you go into the process thinking ‘I’ve got to make this right for everyone and I’ve got to get everyone to like what comes out of this green belt review,’ you will set yourself up to fail.
"The most important thing is to be happy yourself that the information you have collected is evidence that you are comfortable with and works for you as an authority," he said.