Lawyers acting for young twins "stopped and searched" at an environmental protest were granted permission to challenge police powers in the high court today after judges ruled the proper policing of large demonstrations was in the public interest.

The twins were aged 11 when police stopped and searched them at a demonstration against the proposed Kingsnorth coal-fired power station in Kent last August. The judges heard how the children, referred to as girl E and boy T for legal reasons, had been left intimidated and shaken. A third protester, David ­Morris, a longstanding environmental campaigner who said he was he was forcibly searched against his will, was also granted review.

The claimants were searched under section 1 of the Police and Criminal Evidence Act 1984, which requires ­officers to have reasonable suspicion that an individual is carrying prohibited weapons or articles that could be used for criminal damage.

They were among 10,000 protesters corralled into airport-style "checkpoints" used for blanket stop and searches of activists entering and leaving the climate camp demonstration. On the section on search slips on which police must give reasons for the searches, the officers had written only "Oasis Kent" and "D".

Lawyers for the three argued that officers were wrong to search them and that "the level of public concern at the policing of demonstrations is unprecedented, particularly following the recent events at the G20 protests".

Ordering a full hearing to go ahead yesterday, the high court judges appeared to agree. Lord Justice Keene said: "It is clear these proceedings raise issues of some general importance. Large demonstrations are a feature of our democracy, and the proper policing of them is itself a matter of some public importance."

The twins had evidence submitted on their behalf by their mother, referred to as "F", who had made arrangements for her children to meet her at the camp. She described in her statement how her son was "crying and shaking" and "very pale" when she first approached the search queues. A female officer told her "unequivocally" that her son had to be searched. His twin sister was searched soon after.

"During their searches the children's bags were looked through thoroughly and they had to stand by while this was happening," she said. "Nothing was seized from either of them." She said her son was particularly distraught over the experience. After overhearing that protesters had stickers confiscated by police, the boy feared that he would "go to prison" because he had a sticker in his bag.

A spokesperson for Kent police said the force would not comment on the case. However, the decision was a setback to the force, which opposed the twins' application in court. The granting of the review could mean a senior officer is cross-examined to justify the blanket searches of peaceful demonstrators.