Eighty mainly elderly people recently jailed in Malawi for up to six years for practising witchcraft should be freed, campaigners say.
George Thindwa from the Association of Secular Humanism told the BBC the convictions were illegal as there was no law against witchcraft.
He said the problem was that many officials were "witchcraft believers".
The justice minister disputed the allegations, saying the justice system was "reputable".
But the BBC's Raphael Tenthani in Blantyre says the widespread belief in witchcraft led the government to set up a committee last year to consider criminalising it.
Under the law as it stands, it is illegal to accuse someone of being a witch.
The public prosecutions office told the BBC that there had been 11 cases brought under the witchcraft act in the last month across the country.
According to their records, this led to the conviction of 61 elderly women, seven elderly men and 18 younger relatives of the other accused. They received sentences of between four and six years in prison for practising witchcraft.
Justice Minister George Chaponda told the BBC that a person could only be found guilty of practising witchcraft if they confessed to being a witch.
But our reporter says the records showed all the suspects had pleaded not guilty.
"We are intervening in this matter because we are concerned we still have prisons in Malawi [with] people being accused of being witches," Mr Thindwa told the BBC's Network Africa programme.
"The courts were wrong 100%, [and] the police, to actually accommodate cases."
Most of those recently sentenced were women usually accused by children of teaching them witchcraft.
Mr Thindwa said they were vulnerable, given no support and the accusations and convictions took place very quickly.
He appealed to the chief justice and inspector general of police to inform their staff that witchcraft cases "should not be entertained".
"The problem is that our police and our courts most of them are witchcraft believers and this belief is very strong here in Malawi."
But Mr Chaponda said as far as he was aware, there was not a problem, and he urged those with complaints to come forward.
"I'm happy the minister has invited anybody with evidence to come forward. We have a complete dossier of the cases we are disputing," Mr Thindwa said. "We'll take the dossier to his office immediately."