In his New Year message to millions of Catholics worldwide on Tuesday, Pope Benedict reaffirmed the status of the family as one of the most important foundations for peace in the world.

The Pope expressed his support for the family in a midmorning mass on January 1, traditionally celebrated within the Catholic Church as World Day of Peace. He later appeared at his window to wave to thousands of believers in St Peter's Square.

"The family is the first and indispensable teacher of peace," he told the crowds.

Although the Pope stopped short of naming specific policies, he criticised political moves in a number of countries to undermine the traditional family.

The UK is among the countries that have introduced legislation conferring legal rights upon same-sex and unmarried couples in recent years.

Pope Benedict said in his New Year prayer for peace that the family was an "irreplaceable" institution and that undermining the traditional family headed by a husband and wife would undermine peace.

"Whoever, even unknowingly, circumvents the institution of the family undermines peace in the entire community," he said.

"Everything that serves to weaken the family based on the marriage of a man and a woman... constitutes an objective obstacle on the road to peace."

Thousands turned out for a pro-family rally in the largely Catholic Spain on Sunday, during which the Pope defended the family in an address via videolink.

He said: "Founded in the indissoluble union between man and woman, it is the place in which human life is sheltered and protected from its beginning until its natural end."