Young Catholic priests who download sermons from the internet to save themselves the trouble of writing their own have been told that they could be prosecuted for plagiarism. The warning was issued by a leading Polish priest, and has been taken up by Catholic newspapers around the world.

Father Wieslaw Przyczyna claims that, on many Saturday evenings, there is a surge of visitors to websites offering ready-made sermons. He believes that the users are internet-savvy young priests who cannot be bothered to compose their own work in time for Sunday service.

The trend has even been picked up by parishioners who download the same sermons and take them to church so that they can follow the priest's words.

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Other Catholics have turned their anger on Fr Przyczyna for drawing attention to the problem, accusing him of "harassing priests and exposing their weaknesses". He, however, is in no mood to back down.

"If a priest takes another person's text and presents it as his own from the pulpit, without pointing out where he got it from, this is unethical and against the law protectting authorship," he told the Catholic News Service.

"Unfortunately, the practice has become common here. People realise priests are often not speaking for themselves but merely reading someone else's sermon.

"Owners of sermon websites have noticed increased use on Saturday nights, suggesting some priests are trying to rescue themselves at the last moment by finding a text to read out at the next day's Mass."

Fr Przyczyna suggested that, even when they are not plagiarising someone else's work, the sermons of many young priests are less than inspiring. "People don't want to hear patriotic, romantic speeches today – they get enough politics from the media and come to church for a break," he said.

"But there's also been a certain jauntiness and superficiality and a tendency for preachers to choose easy options. The homilies are often unreal and don't deal with issues affecting the lives of real congregations. Priests should speak to people as they really are, not virtual people."

Fr Przyczyna, who heads the religious communication department at the Krakow Papal Theology Academy, has co-authored a book, To Pinch or Not to Pinch with Tomasz Naganowski, a specialist in press law. The book warns that publicly using texts without permission or acknowledgement could lead to prosecution and up to three years in jail. It urges seminaries to instruct student priests on copyright law as part of their training.