Padre Pio, Italy's most-loved saint, faked his stigmata by pouring carbolic acid on his hands, according to a new book.

The Other Christ: Padre Pio and 19th Century Italy, by the historian Sergio Luzzatto, draws on a document found in the Vatican's archive.

The document reveals the testimony of a pharmacist who said that the young Padre Pio bought four grams of carbolic acid in 1919.

"I was an admirer of Padre Pio and I met him for the first time on 31 July 1919," wrote Maria De Vito.

She claimed to have spent a month with the priest in the southern town of San Giovanni Rotondo, seeing him often.

"Padre Pio called me to him in complete secrecy and telling me not to tell his fellow brothers, he gave me personally an empty bottle, and asked if I would act as a chauffeur to transport it back from Foggia to San Giovanni Rotondo with four grams of pure carbolic acid.

"He explained that the acid was for disinfecting syringes for injections. He also asked for other things, such as Valda pastilles."

The testimony was originally presented to the Vatican by the Archbishop of Manfredonia, Pasquale Gagliardi, as proof that Padre Pio caused his own stigmata with acid.

It was examined by the Holy See during the beatification process of Padre Pio and apparently dismissed.

Padre Pio, whose real name was Francesco Forgione, died in 1968. He was made a saint in 2002. A recent survey in Italy showed that more people prayed to him than to Jesus or the Virgin Mary. He exhibited stigmata throughout his life, starting in 1911.

The new allegations were greeted with an instant dismissal from his supporters. The Catholic Anti-Defamation League said Mr Luzzatto was a liar and was "spreading anti-Catholic libels".

Pietro Siffi, the president of the League, said: "We would like to remind Mr Luzzatto that according to Catholic doctrine, canonisation carries with it papal infallibility.

"We would like to suggest to Mr Luzzatto that he dedicates his energies to studying religion properly."