Praise be to Allaah.
It is prescribed for Muslims who have the misfortune to live in kaafir states to unite, to form bonds amongst themselves and cooperate with one another, whether that is in the name of Islamic parties or Islamic organizations, because that is a kind of cooperating in righteousness and piety
And Allaah is the Source of strength. May Allaah send blessings and peace upon our Prophet Muhammad and his family and companions.
From Fataawa al-Lajnah al-Daa'imah, 23/407.