The Society for the Protection of Unborn Children (SPUC) is calling upon family campaigners around the world to resist David Cameron's plans to export same-sex marriage.
The Prime Minister revealed this week that he wants the team of ministers and officials who worked on the bill to legalise gay marriage in Britain to now work on encouraging other countries to pass similar laws.
Mr Cameron said the bill team could "take it around the world".
"Many other countries are going to want to copy this," he said.
"There's a lot more work to be done as Britain in the Commonwealth, talking to our Commonwealth partners about decriminalising homosexuality in various countries."
SPUC said it would be contacting church leaders, politicians and family campaigners worldwide to alert them to the British Government's plans and ask them to raise their concerns with the British embassies in their countries.
"From the very start of his prime ministership, Mr Cameron and his government have been obsessed with promoting the culture of death around the world," said SPUC chief executive John Smeaton.
"This includes spending hundreds of millions of pounds on the promotion of abortion and contraception. People anxious to defend life and family in their countries must warn their fellow citizens about these insidious activities of British government officials."