Growers will have to accept that some sites are not suitable to install polytunnels because of public opposition, the shadow ­environment secretary Peter Ainsworth has said.

"We support British growers and are pleased that this sector has witnessed some of our most successful rural-based businesses," he told the NFU. But such sites should be avoided, he added.

He criticised the government's failure to clarify the planning law on polytunnels, but welcomed plans to seek clarity in the courts.

The NFU said it regretted the overly close focus on the potential impact of polytunnels on property prices.