The head of the Catholic Order of St Augustine – of which Martin Luther was once a part – has offered a stinging rebuke of the Protestant reformer, describing him as 'obstinate, intolerant, abusive and rude'.

Fr Alejandro Moral Antón OSA, the Prior General of the Augustinian Order, wrote an extensive public letter to brothers and sisters of the monastic order examining the legacy of Martin Luther, who was a part of the mendicant group before finally abandoning his religious habit in 1524.

Luther's rebellion ushered in a 'true religious crisis' that 'brought about the rupture of Western Christianity', Fr Antón wrote.

'The damage done to the Order and to religious life in Germany was enormous. Luther was our brother for a time and shared our charism, but he himself stood outside the Order with his choices, his initiatives, and his decisions.'

The order has 'no reason to celebrate the 500th anniversary of the beginning of the Reformation but, yes, to commemorate it.' Fr Antón listed positive consequences of Luther's reforms, such as 'the revalorisation of the individual, the reaffirmed confidence in God, the centrality of Sacred Scripture, the bringing of the liturgy closer to the people, the development of a sense of community, a healthy secularity, and the need for reform, understood as a return to the essentials'.

However, he added that Luther was also compromised by 'nationalism and anti-Semitism', both of which have 'cast their black shadow on the history of the last centuries'.

Fr Antón expanded on Luther's character flaws: 'Obstinate and inflexible, passionate and vehement, Luther used biting expressions against those who opposed him, becoming abusive and rude. Often, he was vexatious and offensive, leading to slander. The one chosen by God, the "prophet of the end times", he considered himself to have the truth and, therefore, responded in aggressive terms to any discrepancy.

'For him, retraction was not possible because he did not assume the possibility of mistake or error... His exaggerated insults and aggressions toward the Church of Rome (papist, according to the particular terminology) are truly sad.'

While the Reformation's emphases on 'always reforming' and putting Scripture in the hands of the laity are to be celebrated, the Prior General was clear that 'the breakup of the Church is an expression of failure for all Christians'.

He concluded that Luther was a 'fascinating' figure who though divisive is worthy of serious study, whose thinking 'returns us to the God revealed in Christ, who is Love and who is concretized in Love'.