The arrests come six months after a crackdown on more than 300 lawyers, activists and associates, and family members in China.
Mervyn Thomas, Chief Executive of Christian Solidarity Worldwide (CSW), told Premier the government needs to "recognise that Christians are no threat to the state of China but in fact the complete opposite, [they] are salt and light in their communities."
The six detained include several employees of Fengrui law firm in Beijing.
Employees of the firm were among the first to be detained in what has been dubbed the "709 crackdown".
Wang Yu, a famous lawyer, disappeared during this clamp down.
Legal assistant Zhao Wei was also formally arrested on suspicion of subversion-related crimes.
Zhao is the assistant of rights lawyer Li Heping, a Christian lawyer who has defended Christians, Falun Gong practitioners and other right defence lawyers.
CSW has reported that the authorities have rejected requests for meetings from Zhao's family and lawyers.
On 9th January, the six month anniversary of the beginning of the crackdown, a statement signed by 108 civil society organisations, called for the release of the lawyers and related individuals still detained in China.
CSW's Chief Executive Mervyn Thomas said: "We are extremely concerned to hear that at least six lawyers and legal assistants are facing such serious charges.
"These individuals are among over 300 lawyers, human rights and religious freedom defenders, and their relatives and colleagues, who have been interrogated, detained, defamed, harassed, and placed under travel restrictions; in the most serious cases they have been forcibly disappeared and held incommunicado for up to six months.
"We join over 100 civil society organisations worldwide in condemning the use of such measures as well as the "collective punishment" of families and friends of prominent lawyers, and the use of the media to attack the reputation of lawyers yet to face trial.
"We call on the Chinese government to uphold rule of law, release those illegally detained and to protect the rights of lawyers to practice, in accordance with domestic and international law."
Listen to Premier's Marcus Jones speak to Mervyn Thomas here: