Is supplicating collectively after the the iqama for prayer prescribed or an innovation, and what is the ruling on praying behind an Imam who does so?

Supplicating at the time of the Iqamah (call to commence prayer) is recommended, as it is one of the occasions when supplications are answered. However, supplicating in a specific, prescribed manner and persistently adhering to it is an innovation (bid'ah). If the Imam repeatedly engages in this act, he should be advised gently to abandon this practice, which has no basis in the Sunnah. Should he insist on it, prayer behind him is valid, because this innovation does not constitute disbelief, although praying behind someone who is not an innovator is preferable.