Steve Timmis and Tim Chester, in their book Total Church, speak on the true nature of church membership:

By becoming a Christian, I belong to God and I belong to my brothers and sisters. It is not that I belong to God and then make a decision to join a local church. My being in Christ means being in Christ with those others who are in Christ. This is my identity. This is our identity. To fail to live out our corporate identity in Christ is analogous to the act of adultery: we can be Christian and do it, but it is not what Christians should do. The loyalties of the new community supersede even the loyalties of biology (Matthew 10:34-37; Mark 3:33-35; Luke 11:27-28). If the church is the body of Christ, then we should not live as disembodied Christians. (p. 41)