Are we "by nature" sinful and unclean?

I belong to a church body that begins each worship service with confession of sins from those who worship, followed by the proclamation of God's forgiveness from the pastor. We have several different formats for the service, and so our confession of sins may be worded slightly differently from one service to the next. In one version, we say we are "by nature" sinful and unclean. This has been a cause for some discussion among the theologians. 

If we are "by nature" sinful and unclean, there are those who see that as indirectly blaming God as creator or criticizing the work of creation. After all, if we are "by nature" sinful, who created that nature? There is an easy-enough response that our current nature is not as God intended, not as we were originally created. Apart from the grace of God, human nature is prone to sin. 

Human nature was never intended to be apart from the grace of God. The relationship of grace between God and man is established in our existence and was never meant to be broken. God, who is present in all things -- who fills all things in every way -- is absent from our thoughts, from our hearts, from our intentions. That is how we are out of step with nature. That is the lack of grace, and why redemption requires God's presence, "God with us", and God's spirit within us. That is what restores the lack inside us, the cure that meets the root cause of the spiritual illness.