The law has the backing of President’s Paul Biya’s party and so might be approved.
Women already face being jailed for between two to six months for having sexual relations outside marriage and men would face the same punishment.
Bar Association head Ngnie Kamga said the law would “take Cameroon backwards and would send more people to prisons”.
The BBC’s Richard Onanena in Cameroon says that women have been jailed for adultery.
“Men having children out of wedlock should be punished because that is evidence of adultery,” one member of parliament, Tomaino Ndam Njoya, is reported to have said during the debate.