A possible landmark deal that would see China and the Vatican come to an agreement on the appointment of bishops would be "absolutely unacceptable", China's most senior Catholic cleric has said.

Cardinal Joseph Zen Ze-kiun, the retired bishop of Hong Kong, told the Wall Street Journal that if the Vatican agrees to let Beijing appoint bishops, the Catholic Church would become "totally subservient to an atheist government".

Relations have historically been strained between the Catholic Church and China's ruling Communist party (CCP) over irreconcilable claims to authority. The Vatican does not accept the validity of episcopal consecrations by the Chinese Catholic Patriotic Association – the government's state-approved Catholic body – while the CCP has strongly opposed Rome's right to ordain Chinese bishops.

An underground Catholic Church refuses to compromise with the state and is loyal only to the Pope. The feud has been ongoing for more than six decades, alongside growing concerns from the CCP about the growth of Christianity in China.

The government has signalled a crackdown on churches, and closely monitors members of even state-controlled institutions.

The new deal would see the Vatican accept eight bishops ordained by the CCP without the Church's permission.

Cardinal Zen accused state-appointed bishops of being "slaves" and "puppets" of the CCP, though he added that they were "very faithful to the Church".

But "with fake bishops you are destroying the Church," he said.

However, though he said Pope Francis – who isn't known to have signed any deal yet – "has no real knowledge of communism" and may make the wrong decision in this case, he will respect his authority.

But Chinese Catholics are "not bound to join the Patriotic Association," the Cardinal added. "You can pray at home if you lose your churches."