The CPRE’s analysis of figures published by the Planning Inspectorate (PINS) shows that 47.9 per cent of councils in England have an adopted plan.
Nearly 30 per cent of local authorities have yet to even publish a plan, according to the figures, while a further 22.9 per cent have published a plan but have yet to formally adopt it.
Under transitional arrangements set out when the National Planning Policy Framework was published in March 2012, councils with local plans adopted since 2004 were told they could continue to give full weight to relevant policies "even if there is a limited degree of conflict" for 12 months.
But following the 12-month transition period, which ends on 27 March, decision-takers must give due weight to relevant policies in existing plans "according to their degree of consistency" with the NPPF, the framework says.
In a statement, the CPRE said that a significant proportion of plans that are already in place could be deemed out of date.
It says that a number of councils have been working hard to update their plans, but resource cuts and wider reforms, including the abolition of regional plans, have made it difficult for many to proceed quickly.
Neil Sinden, director of policy and campaigns at the CPRE, said: "It is not too late for the government to take action to ensure their planning reforms do not result in a rash of damaging development and irreversible loss of countryside.
"So today we are asking planning minister Nick Boles to extend the transitional period by at least another 12 months and ideally 18 months.
"Of those councils with no plan, 23 per cent have started the process of having a plan adopted; this extra time would therefore allow a significant proportion of councils to get their plans in place. This will help ensure that local people have a say on what development happens in their area."
But Boles said: "The CPRE’s figures are misleading. Seven out of ten local councils now have published local plans compared to two out of ten previously, and there is good progress across the remainder. Up to date local plans provide certainty to both local residents and local firms, and we have offered councils a range of practical assistance to help them get up to speed.
"There are strong protections in place for the green belt, open countryside and areas of outstanding natural beauty when considering planning applications against the planning framework as a whole."
This week industry body the Home Builders Federation said that it had expanded its planning team so that it can represent housebuilders at all forthcoming local plan examinations.
View CPRE's map of local plan coverage in England here.