With kinky nuns in lingerie plus tattooed and near-naked Christs, two recent exhibitions in Madrid have enraged Catholics and conservatives who brand them blasphemous.

Catholic group AES called a demonstration for Friday evening outside the Fresh Gallery in Madrid against its latest exhibition: "Obscenity", a collection of photographs by Canadian artist Bruce LaBruce.

The 50 pictures on display include a portrait of Spanish actress Rossy de Palma in a black and white habit and see-through corset with a rosary between her teeth.

One shows a well-known singer, Alaska, dressed as a sexy saint with a communion wafer on her tongue, while in another she hugs a tattooed Christ to her breast in a kinky tribute to Michaelangelo's "Pieta" sculpture.

In a separate exhibition at the national Spanish Theatre, a photograph of an actor posing naked as Christ with a religious painting over his privates was branded blasphemous in a petition signed by over 40,000 Spaniards last month.

After the opening of LaBruce's show this week, AES called for a demonstration "against blasphemy" outside the gallery on Friday, "in defence of our Christian roots and the Catholic faith".

"Blasphemous provocation threatens again," a conservative campaign group, Make Yourself Heard, said on its website, in a statement that described the offending works in detail.

"Gay-looking angels encouraging lechery, lascivious nuns posing in underwear, revelling with crucifixes or cradling a tattooed Christ between their breasts... this is the new content of the provocative exhibition 'Obscenity,'" it complained.

The Francisco Franco Foundation, a group that campaigns to preserve the memory of Spain's former dictator, branded the exhibition "a virulent and morbid attack on the Catholic religion".

LaBruce, 48, whose work has often sparked protests and censorship, wrote on the gallery's website that "the lives of the saints are full of ecstatic acts of sublimated sexuality".

"'Obscenity' presents a series of portraits that illustrate this most holy convergence of the sacred and the profane."

In the show at the theatre running until February 26, the offending image shows an actor preparing for his role as Christ with a reproduction of "Christ Crucified" by the Spanish painter Diego Velazquez covering his genitals.

Conservative religious rights group Mas Libres, a branch of Make Yourself Heard, urged Madrid city hall to ban that work, by Spanish photographer Sergio Parra, from that municipal exhibition. The city hall refused.

In a separate art controversy, the Franco Foundation also complained about an exhibit at this week's ARCO contemporary art fair in Madrid: "Always Franco" by Eugenio Merino, a sculpture of the dictator inside a soft drinks fridge.

"The work generates hate and confrontation," the vice president of the foundation, Jaime Alonso, was quoted as saying by Spanish media, threatening to sue Merino as well as the organisers of the fair.

"We can't ignore this because otherwise we will have increasingly coarse and scatological provocations."