Some 30,000 Muslims from 100 countries will gather for the three day event, known as Jalsa Salana, in Hampshire.
He said attackers Khalid Masood, Khuram Butt, Rachid Redouane and Youssef Zaghba had “no knowledge of Islam”.
The Caliph said: “Recently, terrorist organisations have started to regularly commit the most barbaric atrocities in Western countries by taking the lives of innocent people. London Terror Attack Floral Tributes at Westminster – 27 March 2017“The terrorists have no knowledge of Islam because otherwise they would realise that the Holy Prophet of Islam forbade the murder of innocent people under any circumstances and even during a state of war.”
The statement comes months after Masood ploughed into pedestrians on Westminster Bridge before fatally stabbing PC Keith Palmer to death outside the gates of Westminster in March.
In June, Butt, Redouane and Zaghba mowed down Saturday night revellers on London Bridge before launching a knife attack on nearby Borough Market.