Just months before the general election the new Pope last night urged New Zealand's leaders to "ensure the question of morality is given ample discussion in the public forum".
He also appeared to hit out at Labour's civil unions legislation.
"There is a great need today to recover a vision of the mutual relationship between civil law and moral law," Benedict XVI told Geoff Ward, New Zealand's new envoy to the Vatican.
"I therefore encourage the people of Aotearoa, through you, Mr Ambassador, to continue to take up the challenge of forging a pattern of life, both individually and as a community, in relation to God's plan for all humanity."
The Vatican's news service reported that he made the comments specifically about New Zealand at a speech to seven new ambassadors to the Holy See.
After welcoming them in French, Pope Benedict said that, through the diplomats, he wished to address their citizens about the civil and religious situation in their countries.
He handed Mr Ward a written message that appeared to target the civil union legislation, which has been criticised by some religious groups as enabling gay marriages.
"New Zealanders traditionally have recognised and celebrated the place of marriage and stable domestic life at the heart of their society and indeed continue to expect social and political forces to support families and to protect the dignity of women, especially the most vulnerable," the Pope said.
"Secular distortions of marriage can never overshadow the splendour of a life-long covenant based on generous self-giving and unconditional love.
"Correct reason" would tell New Zealanders that the future of humanity was passed on by way of the family, which offered society a secure foundation for its aspirations.