The Rt Rev. Mark Davies will express his concern to more than a thousand English pilgrims gathered at the Marian shrine of Lourdes, France, on Monday.
He said Christianity might be caught-up in measures to combat non-violent extremism if there is no clear definition of what constitutes such dangerous extremism.
He said although Theresa May's new counter-extremism measures aim to tackle terrorist ideology, it could also be misused to ensnare peaceful Christians who disagree with secularist ideologies often sponsored by the state.
The Bishop will discuss what he deems are destructive extremism of these ideologies towards marriage, the family and medical ethics.
Bishop Davies will tell pilgrims from the Dioceses of Shrewsbury and Salford that Christians are extreme only in their following of Christ and in all that contributes to the good of society.
He claimed Christians should be extreme when it comes to "charity, of virtue, of grace, of unswerving adherence to goodness and truth, to the high goal of holiness in which lies our ultimate happiness".
Bishop Davies cited a poll commissioned by the Evangelical Alliance that found 28 per cent of people considered Jesus Christ to be an extremist.
In the wake of the recent terrorist attacks in Westminster, Manchester, London Bridge and Finsbury Park, the Government's counter-terrorism strategy, which includes counter-extremism, came into the spotlight.
The 2017 Queen's Speech announced the establishment of a new Commission for Countering Extremism, as well as a review of counter-terrorism powers and a commitment to tackling online extremist content.
