The six-year-old daughter of Christian Chinese human rights lawyer Li Heping, who has been uncontactable and held in black jail since he disappeared in July 2015, is determined that she can rescue her dad.

In a moving interview with the Guardian, Li Jiamei's mother, Wang Qiaoling, said: "She's small. She misses her dad. I tell her I miss him too and that we must try to get through this together."

China has been accused of a severe crackdown on churches, most significantly in the eastern coastal province of Zhejiang, where up to 1,700 churches have been demolished or had their crosses removed since late 2013.

This has intensified over the past year and combined with an increased crackdown on human rights lawyers. More human rights defenders have been detained or are missing under two years of President Xi Jinping's leadership than in the previous two decades. Many of them worked on behalf of churches targeted by the demolition campaign.

At least 10 detainees in Zhejiang remain in so-called 'black jails', which have no legal status, and in which torture is common.

Wang, who is a devout Christian, told the Guardian that she finds comfort in her relationship with God despite her family's difficult circumstances.

"We know that in all things God works for the good of those who love him, who have been called according to his purpose," she said, quoting from Paul's letter to the Romans.

Li was arrested on July 10, 2015, and in January this year Chinese authorities disclosed that he had been imprisoned in Tianjin on subversion charges that carry a potential life sentence.

Wang, a lawyer herself, rejects the charges as a "farce".

"The entire process has been unlawful from the very start," she said.

She recalled that on the day of Li's arrest her daughter "begged her father to take her to work. And then it happened – that was the day."

When he arrived at work, with his daughter with him, Li's car was surrounded by police. He apparently refused to be taken before safely returning his daughter home.

Wang told the Guardian she initially did not realise the severity of the situation, as her husband had been detained, tortured and abducted previously due to his decade-long career in human rights.

"I thought they might just have summoned him for a chat," she said.

"I miss him so much but I have decided to miss him in a happy way," she said. "I can miss him and still be happy at the same time. I can be happy in standing up for our rights. And I can also try to make others happy. That is a choice we can make. As for having our families taken away from us, we don't have any choice about that."

Wang makes regular trips across China to meet with the spouses of other jailed attorneys for support and continues to protest their arrests. She was taken into custody herself on Monday following the latest protest.

Li Jiamei, meanwhile, has decided to follow in her father's footsteps. Wang recalls her telling a friend that when she grows up, "I want to be a human rights lawyer".