The BBC reports that 13 councils have a time of prayer before the formal start which means it is not formally classed as an agenda item. It also means that people of other faiths are not required to participate. Only 5 Welsh councils do not hold any prayers.
Campaigners have already called for the practice to be ended.
The National Secular Society (NSS) said councils "shouldn't be clubs for Christians."
Nevertheless, none of the councils have changed their position in over a year.
The Church in Wales said prayer or reflection "could be hugely beneficial".
They also said councillors could benefit from prayer or reflection before making "decisions which will affect many people".
Denbighshire is the only council that holds a formal prayer at the beginning of full council meetings.
A spokeswoman said: "Those of us with a faith may give thanks for the opportunity to make a difference and ask for God's guidance on our decisions. Those without a faith may appreciate a moment of quiet to reflect on the task ahead and remind us of our common purpose."
An act covering England says council meetings "may include time for prayers or other religious observance, or observance connected with a religious or philosophical belief".
There is no equivalent act in Wales and the Welsh Local Government Association said individual councils were not issued guidance on the matter and could use their own discretion.