The group, part of the Love Makes A Way movement, was arrested after refusing to leave Foreign Minister Julie Bishop's office in Perth where they were conducting a prayer vigil against children being held in immigration detention.

One of the protesters, Westcity Church of Christ pastor Jarrod McKenna, said police conducted a strip search at the Perth watchhouse despite pleas from the protesters that they were unnecessary.

"While I stood there naked in front of those two police officers they asked, 'Lift up your testicles'. I was informed this was to check I wasn't hiding a weapon," Pastor McKenna said. "While the thought that anyone would think I could conceal a weapon under my wedding tackle would normally be flattering, I seem[ed] to be in a situation where humiliation and intimidation seemed to be the intention."

Pastor McKenna said the group was taking legal advice. "This abuse must be challenged and, with lawyers from around Australia volunteering their services, we will [challenge it]," he said.

Executive director of the Human Rights Law Centre, Hugh de Kretser, said reports of peaceful protesters being strip-searched were "deeply concerning".

"Police can't strip search someone unless it's reasonably necessary and even then they need to do the strip searches in the least intrusive way," he said. "It would be clearly unlawful if police used the strip searches to humiliate or punish peaceful protesters."

WA police declined to confirm whether strip searches were conducted. "The group were fully advised they would face charges and as such undergo standard procedures at the Perth watchhouse if they did not comply," a spokesperson said.

Another protester, Anglican priest Reverend Lorna Green, said while she was angry about being searched, it allowed her to empathise with the asylum seekers for whom she was advocating. "I was outraged to be stripped naked to be searched for drugs and firearms, but I'm even more outraged at the way our government is treating helpless babies [in detention]," she said.

Reverend Green was undeterred by the repercussions of her actions. "If it means being arrested or being strip-searched and possibly getting a criminal record, then that's the price that I … [am] prepared to pay," she said.

Love Makes A Way says it will continue to protest against the government's policies until all children are released from immigration detention in Australia and Nauru.

The group was formally charged with trespass and will appear in court.