(By Kate Carlisle) Rome, July 15 - The Democratic Party (PD) on Monday called for Deputy Senate Speaker Roberto Calderoli to quit for saying Italy's first black minister looked like an orangutan, while Premier Enrico Letta said the episode was "shameful". The top party in Italy's grand coalition said the Northern League bigwig's bid to "minimise" his remarks against Congo-born Integration Minister Cecile Kyenge could not excuse them. "Enough already," the PD said in a note after Calderoli claimed he had been joking and he was known for comparing ministers to animals. "We can't leave scope for inexcusable racism, insults, the instigation of the worst instincts," the PD said. Letta called on the head of Calderoli's party, Lombardy Governor Roberto Maroni, to intervene. Letta appealed to Maroni on Monday to quickly close the "shameful chapter" caused by Calderoli that has hit the foreign press in "all of Europe". On Monday Calderoli told the Italian daily paper Il Corriere della Sera that his comments Kyenge, slammed as the umpteenth racist insult by anti-immigration Northern League members, were born from his "love for animals". The Northern League heavyweight brushed off his comparison of the Congolese-born minister saying it was "an aesthetic judgment, not meant to be racist". Calderoli was quoted on Sunday as saying :"When I see her (Kyenge's) pictures, I can't help but think of her resemblance to an orangutan" while speaking at town festival in Carroccio a Treviglio near his home city of Bergamo. Despite first saying that his comments were part of a larger discussion on immigration, later Sunday Calderoli phoned Kyenge to apologize. Maroni said that the Senator had "done well to apologize," but that his comments had been fueled by "immigration policies proposed by Kyenge that are not only wrong, they contribute to the uncontrollable influx of immigration" into Italy. Kyenge has been the subject of racist abuse, mostly from the anti-immigrant League, since her appointment in the PD's unprecedented coalition with its traditional foe, the People of Freedom (PdL) Party of ex-premier Silvio Berlusconi, in April. Kyenge has been pushing to ease immigration norms in Italy and for children born to migrants in the country to be automatically granted Italian citizenship. Italian President Giorgio Napolitano spoke out on Sunday against the slur, as well, expressing "indignation" at the latest attack on Kyenge. However, League Deputy Secretary Matteo Salvini struck back saying: "I am angry at those who are indignant. It would be best if Napolitano shuts up," Salvini said. Yet another Northern League member added fuel to the fire when he said that in the comparison to Kyenge, the "real victim is the orangutan". Regional councillor and Veneto League member Daniele Stival said on Facebook that an orangutan is "one of God's creatures" and should not be compared to a "Congolese minister". Stival removed the post shortly after and said that he had made a mistake. The PD said that Calderoli's comments were already spurring copycat incidents like the rightist Forza Nuova Party dangling nooses during a visit by Kyenge to the Abruzzo coastal city of Pescara Monday. Calderoli has a history of xenophobic stunts, including a 2006 TV appearance wearing a T-shirt bearing cartoons of the prophet Mohammed which sparked riots in Libya that left 11 dead. He was forced to resign as reforms minister at the time. Later that year he made racist remarks about the France team that lost to Italy in the 2006 World Cup Final, saying it was because the opposing team was stacked with "negroes, Muslims and communists". In 2007 he campaigned against a planned mosque in Milan, leading a pig over the site. PD Senator Sergio Lo Giudice responded on Monday with an official complaint filed with Italy's anti-racial discrimination body against the deputy Senate speaker. "This morning I sent Italy's National Office against Racial Discrimination (UNAR) a formal communication about the disturbing incident of racially motivated offenses against Minister Cecile Kyenge," Lo Giudice said. "I felt that it was my duty to report this episode that, due to the institutional source it comes from, is particularly serious and reflects conduct based on the idea of racial superiority and discrimination on the basis of ethnic backgrounds," Lo Giudice said.