Italian judge has ordered a priest to appear in court this month to prove that Jesus Christ existed.

The case against Father Enrico Righi has been brought in the town of Viterbo, north of Rome, by Luigi Cascioli, a retired agronomist who once studied for the priesthood but later became a militant atheist.

Signor Cascioli, author of a book called The Fable of Christ, began legal proceedings against Father Righi three years ago after the priest denounced Signor Cascioli in the parish newsletter for questioning Christ’s historical existence.

Yesterday Gaetano Mautone, a judge in Viterbo, set a preliminary hearing for the end of this month and ordered Father Righi to appear. The judge had earlier refused to take up the case, but was overruled last month by the Court of Appeal, which agreed that Signor Cascioli had a reasonable case for his accusation that Father Righi was “abusing popular credulity”.

Signor Cascioli’s contention — echoed in numerous atheist books and internet sites — is that there was no reliable evidence that Jesus lived and died in 1st-century Palestine apart from the Gospel accounts, which Christians took on faith. There is therefore no basis for Christianity, he claims.

Signor Cascioli’s one-man campaign came to a head at a court hearing last April when he lodged his accusations of “abuse of popular credulity” and “impersonation”, both offences under the Italian penal code. He argued that all claims for the existence of Jesus from sources other than the Bible stem from authors who lived “after the time of the hypothetical Jesus” and were therefore not reliable witnesses.

Signor Cascioli maintains that early Christian writers confused Jesus with John of Gamala, an anti-Roman Jewish insurgent in 1st-century Palestine. Church authorities were therefore guilty of “substitution of persons”.

The Roman historians Tacitus and Suetonius mention a “Christus” or “Chrestus”, but were writing “well after the life of the purported Jesus” and were relying on hearsay.

Father Righi said there was overwhelming testimony to Christ’s existence in religious and secular texts. Millions had in any case believed in Christ as both man and Son of God for 2,000 years.

“If Cascioli does not see the sun in the sky at midday, he cannot sue me because I see it and he does not,” Father Righi said.

Signor Cascioli said that the Gospels themselves were full of inconsistencies and did not agree on the names of the 12 apostles. He said that he would withdraw his legal action if Father Righi came up with irrefutable proof of Christ’s existence by the end of the month.

The Vatican has so far declined to comment.

THE EVIDENCE

• The Gospels say that Jesus was born to the Virgin Mary in Bethlehem, grew up in Nazareth, preached and performed miracles in Galilee and died on the Cross in Jerusalem

• In his Antiquities of the Jews at the end of the 1st century, Josephus, the Jewish historian, refers to Jesus as “a wise man, a doer of wonderful works” who “drew over to him both many of the Jews and many of the Gentiles”

• Muslims believe Jesus was a great prophet. Many Jewish theologians regard Jesus as an itinerant rabbi who popularised many of the beliefs of liberal Jews. Neither Muslims nor Jews believe he was the Messiah and Son of God

• Tacitus, the Roman historian who lived from 55 to 120, mentions “Christus” in his Annals. In about 120 Suetonius, author of The Lives of the Caesars, says: “Since the Jews constantly made disturbances at the instigation of Chrestus, Emperor Claudius expelled them from Rome.”