Ala Hazrat Imam Ahmad Raza Khan was asked a lengthy question regarding Salah behind an individual who classes a Wahabi and a Sunni scholar as similar and alike.
He answers:
An individual who regards the Wahabis and the scholars of the Ahl al-Sunnat as similar and alike - his statement is enough to take him out of the folds of Islam. To pray Salah behind such an individual (who utters such statements) is invalid [Batil]; similar to praying behind Hindus and Christians.
It is in Fath al-Qadeer: Imam Muhammad narrates from Imam Abu Hanifa and Imam Abu Yusuf that Salah is not permitted behind the Ahl al-Bid'at (people of innovation) and deviants.
[Fatawa Razwiyyah - Volume 6 - Pages 637 & 638]
Translated by Muhammad Kalim (Preston)
www.thesunniway.com