"Party political activities, such as public meetings, demonstrations, rallies, debates inside premises, which are after all every citizen's right, have been suspended until the next elections," said a letter penned by the country's Catholic bishops.
Denouncing "violations of the constitution and national laws," the bishops pointed to the temporary shutdown of some media outlets, saying it amounted to "restricting citizens' right to be informed" and hence freedom of expression.
The episcopal letter warned such a political climate would only foment "division and hatred."
"If we allow this to continue, we should not be surprised if we find ourselves embroiled in worse conflicts which will destroy the basis of peace and national unity," it said.
In recent months, the church has come under fire for its silence in the face of Magufuli's "dictatorial bent" and particularly over its failure to address the attempted murder of senior opposition lawmaker Tundu Lissu in September.
Lissu was shot at his home in the capital Dodoma and was rushed to the Kenyan capital Nairobi where he was in intensive care for several months before being transferred to a hospital in Brussels.
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His CHADEMA party has accused the government of trying to assassinate Lissu, who is also president of Tanzania's bar association.
Magufuli, nicknamed the Bullzozer, took office in 2015 promising to tackle corruption.
But detractors say he is autocratic and has clamped down on freedom of expression with opposition party meetings routinely banned and several newspapers shut while several journalists and artists have suffered death threats for criticising his regime.