Are those Imams true Muslims who in their supplications ask Allah to forgive them for the sake of Mohammed (pbuh). Is it not like treating Mohammed (pbuh) as a partner in the power of Allah? Will congregational prayers behind such mushrik-like Imams be valid?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

We previously clarified the rulings related to making Tawassul through the Prophet, sallallaahu ‘alayhi wa sallam, in Fatwa 84006. If it belongs to the permissible form of Tawassul, the one who makes it is a Muslim and performing prayer behind him is permissible. But if it belongs to the religiously-innovated form of Tawassul, the one who makes it is also a Muslim. Nevertheless, it is not permissible to stop performing prayer behind the doer of religious innovations if there is nobody else available (to perform prayer behind him). However, if there is someone else available, it is preferable to perform prayer behind him instead.

On the other hand, if the man's Tawassul belongs to the polytheistic form, it is not permissible to perform prayer behind him. For further information, see Fatwa 82654.

In any case, if a Muslim commits any of the religious innovations related to actions or belief, it is obligatory to advise him and explain to him the truth. It is not permissible to declare a Muslim a disbeliever even if he commits an act of disbelief unless certain conditions are met, as was previously clarified in Fataawa 91567 and 84943.