A senior employee of a US Catholic charity has resigned after a conservative Catholic organisation mounted a campaign against him because he was gay and had entered into a same-sex marriage.

The incident has outraged Catholic Relief Services, for which Rick Estridge had worked for 16 years, eventually as vice president for overseas finance.

Estridge was attacked online by The Lepanto Institute, which describes itself as "dedicated to the defense of the Catholic Church against assaults from without as well as from within". It posted a copy of his marriage certificate as well as photographs and other details from his Facebook account. Estridge's employment at CRS, it said, made it "very difficult to trust the 'Catholic Identity' of the organisation".

Estridge, who is not Catholic and whose responsibilities were purely technical, resigned because of the stress the situation had caused him and his family. He released a statement thanking CRS for its support and saying: "I continue to have full faith in CRS' leadership and the organisation as a whole. I thank my team and the global finance community for their hard work and dedication and have every belief that they will continue to serve with excellence."

A CRS statement said that it "respects Mr. Estridge's decision and thanks him for his service. He has done a tremendous job during his years at CRS and will be missed. We are grateful that he has agreed to be available as needed for consultation to ensure a smooth transition."

But it added: "CRS also wants to express its strong objection to these types of attacks and the tactics of the groups which launch them. This highly personal, public critique broadcast Mr. Estridge's home address and used derogatory terms that are now part of the online record. This has caused great pain for many people.

"As a Catholic agency, CRS is committed to treating all people with the respect and compassion they deserve as children of God. We detest hurtful campaigns that do not build up, but undermine, individuals and Church agencies carrying out the mission of bringing the love of Jesus Christ to those who are suffering."

It stressed the organisation's fidelity to its Catholic identity, saying that it worked "in countless ways to support marriage and family life".