A German bishop has flown - reportedly with a budget airline - to the Vatican in Rome to discuss his lavish spending.

Franz-Peter Tebartz-van Elst - dubbed the "Luxury Bishop" - is facing calls for his resignation after spending 31m euros (£26m; $42m) on his residence.

He is also accused of lying about the over-spend on the property in Limburg.

In Rome, he will meet the head of the Catholic Church in Germany, Archbishop Robert Zollitsch. It is not clear if Pope Francis will intervene.

Since taking office in March, Pope Francis has urged the Church to promote a lifestyle of frugality and simplicity.

The allegations have stoked controversy among Catholics in Germany, where Martin Luther launched the Reformation in Europe five centuries ago in response to what he said were excesses and abuses within the Church.

German Catholics also pay a compulsory tax to the Church as part of their income tax, and many are shocked by the apparent financial waste - prompting some to stage demonstrations outside the bishop's residence in Limburg, a town in Hesse near Frankfurt-on-Main.

"The bishop has made it clear that any decision about his service as a bishop lies in the hands of the Holy Father (Pope Francis)," said a statement issued by the diocese on Saturday.

"The bishop is saddened by the escalation of the current discussion. He sees and regrets that many believers are suffering under the current situation," it said.

'Sounds frightening'

Bishop Tebartz-van Elst is also accused of twice lying under oath about a flight he took to India on a trip to visit poor children.

The 53-year-old had filed a civil court claim against Der Spiegel magazine, which is based in Hamburg, for reporting that he had flown first-class on the trip.

After being forced to print a retraction, the magazine filed a legal complaint of its own. As evidence, it published mobile phone video (in German) of its interview with Bishop Tebartz-van Elst, in which he clearly stated that he had flown business class.

Asked by the German daily Bild about the high cost of his new residence, the bishop said: "I understand that the high cost of 31m euros sounds frightening. Those who know me know that I don't have a pompous lifestyle."

Archbishop Zollitsch said he had set up a commission to investigate the finances of Limburg diocese.

He said he would "speak to the Holy Father and the relevant people" about the issue in Rome.