A anti-gay Christian group is campaigning to have an iPhone app against gay marriage reinstated.

Apple removed the Manhattan Declaration app from its iTunes store last week after media attention but the Christian group is calling for supporters to sign a petition to have it returned to the site.

The Manhattan Declaration is a manifesto released in 2009 by Christian and Catholic leaders which rails against the “erosion” of marriage.

According to the group’s website, 15,500 people have signed the online petition – more than twice the number who signed a petition to have the app removed.

The declaration says that gay relationships are “immoral” and that same-sex marriages are equivalent to sanctioning incest.

However, the group behind it says that it is “civil, reasoned, and respectful” and does not “promote hate or homophobia [and] is not anti-gay”.

The app asked users whether they agreed with four statements on abortion and same-sex marriage and those who answered that they are pro-choice and pro-gay marriage were told that they were incorrect. It also had links to read and sign up to the full declaration

Apple initially rated the app 4+ , meaning that it contains “no objectionable content” but removed it over the Thanksgiving weekend.

Apple spokeswoman Natalie Kerris told CNET: “We removed the Manhattan Declaration app from the App Store because it violates our developer guidelines by being offensive to large groups of people.”