Around 70 placard waving members of a group called Anonymous, many of them wearing full gowns and masks, gathered outside the Church of Scientology headquarters on Ethel Street, on Saturday.
The Church of Scientology has Tom Cruise and John Travolta among its followers.
The protesters said they were concerned over the way it recruited members.
But the Church of Scientology responded by comparing Anonymous to “terrorists”.
The protest, dubbed Operation Reconnect, comes after the Birmingham Mail revealed that the Church is thought to have paid as much as ?4.25million to buy the old Pitmaston building, in Moor Green Lane, in Moseley, to use as its Midlands HQ.
It will become the organisation’s second biggest base in the UK.
Protest supporter Dr Martin Poulter said: ” The information we have from Birmingham tells us that while Scientology is declining in the rest of the country, it is growing in Birmingham.
“That is suggested by them getting a property in Birmingham. People should be warned about Scientology increasing their operations here.”
Dr Poulter also said Anonymous was concerned about the Church’s recruitment methods, which he claimed involved taking large sums of money, and policy of disconnecting members from their family and friends.
“There is no science behind their theories,” he claimed.
But a Church of Scientology spokesman called Anonymous “anti-freedom of religion and anti-free speech”.
In a statement, the spokesman said: “Anonymous is perpetrating religious hate crimes against Churches of Scientology and individual Scientologists for no reason other than religious bigotry.
“The terrorist crimes of Anonymous should be condemned.”
Original title: Demo against church move.
Note: [Church of Scientology] in brackets as the phrase apparently ‘fell away’ from the original online text.