Vatican City, December 14 - Pope Benedict XVI came under fire from gay-rights campaigners on Friday for suggesting that attempts to give gay unions the same status as marriages between men and women pose a threat to justice and peace. "There is also a need to acknowledge and promote the natural structure of marriage as the union of a man and a woman in the face of attempts to make it juridically equivalent to radically different types of union," the pope said in his message for World Day of Peace 2013, which was presented by the Holy See on Friday. "Such attempts actually harm and help to destabilize marriage, obscuring its specific nature and its indispensable role in society. "These principles are not truths of faith, nor are they simply a corollary of the right to religious freedom. "They are inscribed in human nature itself, accessible to reason and thus common to all humanity. "The Church's efforts to promote them are not therefore confessional in character, but addressed to all people, whatever their religious affiliation. "Efforts of this kind are all the more necessary the more these principles are denied or misunderstood, since this constitutes an offence against the truth of the human person, with serious harm to justice and peace". Benedict's comments led to a wave of criticism from gay-rights groups and some some centre-left politicians. Flavio Romani, the head of the Arcigay association, said that the message "arms the homophobes of all countries with an invitation to take part in a crusade against marriage between people of the same sex". Nichi Vendola, the openly gay governor of Puglia and the leader of the left-wing SEL party, was dismayed. "I'd like to ask the Catholic Church why it is trying to run away from dialogue, from listening, from debate," he said. "At the end of the day, even the inhabitants of the Holy See have often made mistakes during the course of history". Anna Paola Concia, a lesbian MP with the main centre-left Democratic Party, echoed those sentiments. "I'd like to ask Pope Benedict XVI and all those who listen to him a question," she said. "What are the battles that have most undermined peace in the history of the world? "Are they the religious wars or the claims of the lesbian, gay, bisexual, and transgender movement, who are only asking to see love between two people of the same sex to be recognised. "The pope has never been so aggressive towards a part of the public. This is certainly one of those comments that go against any Christian message. "We must be very careful. The seed of hate is contagious and we gay citizens know this as we have been victims of it". The leader of the small Socialist Party (PSI) criticised the head of the Catholic Church too. "It's the pope who is using the words of the Inquisition, which undermine peace and the fundamental rights of man," said Riccardo Nencini. The pope also said in his message that people cannot call themselves peace-lovers if they are in favour of abortion and euthanasia. "Anyone who loves peace cannot tolerate attacks and crimes against life," the said. "Those who insufficiently value human life and, in consequence, support among other things the liberalization of abortion, perhaps do not realize that in this way they are proposing the pursuit of a false peace "Indeed how could one claim to bring about peace, the integral development of peoples or even the protection of the environment without defending the life of those who are weakest, beginning with the unborn. "Every offence against life, especially at its beginning, inevitably causes irreparable damage to development, peace and the environment. "Neither is it just to introduce surreptitiously into legislation false rights or freedoms which, on the basis of a reductive and relativistic view of human beings and the clever use of ambiguous expressions aimed at promoting a supposed right to abortion and euthanasia, pose a threat to the fundamental right to life". The pope's message for World Day of Peace 2013, which takes place January 1, is entitled Blessed are the Peacemakers.