In October 2011 Ms Tymoshenko was sentenced to seven years in prison for abuse of power.
Her supporters claim the sentence was political revenge by President Yanukovych.
In a joint letter the leaders of the Ukrainian Greek Catholics, Roman Catholics, Baptists and the self-proclaimed Kievan Patriarchate of the Orthodox Church called for forgiveness, mercy and love for others.
"Pardoning Yulia Vladimirovna Tymoshenko and releasing her from prison would celebrate these godly virtues," they wrote.