China Aid fears Chinese Christians will suffer under a "shift" in government policy, away from encouraging believers to "mutually adapt with socialism" to forcing them to conform to the government's agenda.
It said: "We have good reasons to worry that the major religions in China, especially house churches and underground Catholic and Protestant churches, will suffer the most unprecedented suppression under the name of the 'transforming into the Communist Party of China' since the Cultural Revolution."
China Aid says a policy of Sinicization - encouraging submission to dominant Chinese state and culture - by president Xi Jinping marks a significant departure from former president Jiang Zemin's approach.
It's released a new report which is warning how the implementation of the newly-revised Regulations on Religious Affairs - which was introduced as a draft in September and is currently awaiting approval - will impact believers.
China Aid is concerned cases such as the removal of crosses from churches in Zhejiang province could become more widespread in China.
It also fears house churches will face increasing pressure to join the state-run Three-Self church movement and religious sites will be compelled to introduce symbols of The Communist Party of China.
China Aid concludes: "The guiding ideology decreed in 2016 that 'religion must persistently follow the path to Sinicization' actually alludes to the subtext that 'all religions have to surrender to the authority and leadership of the Chinese Communist Party'."
Setting out its agenda for 2017, China Aid said it will monitor closely the situation for Christians in China and expand its Bible classes.