(RNS) InterVarsity Christian Fellowship USA (IVCF), a large ministry operating on 667 college campuses nationwide, faced widespread backlash after it announced last week it would begin "involuntarily terminating" employees who hold a theological position supporting gay marriage. But the heat is rising today as influential authors and InterVarsity alumni are now publicly protesting the decision.

In a public letter obtained by Religion News Service, more than 50 authors in InterVarsity's publishing house stable including Shane Claiborne, David Dark, Christena Cleveland, Ian Morgan Cron, and Chris Heuertz are calling on IVCF head Tom Lin to immediately replace the policy with one that makes space for opposing views. The letter indicates that the signers "do not all share the same theological or political views" but "are united in our concern for the dignity and care of our fellow Christians whose jobs are threatened by your policy."

Chris Heuertz, co-founder of the Gravity Center in Omaha and author of multiple books with InterVarsity Press, sent the letter to Tom Lin via email on Tuesday afternoon. He made clear that the letter was drafted in the spirit of friendship and sadness, not anger.

"As friends of IVCF, this letter comes from a place of deep sorrow," Heuertz said. "This is not an attack on IVCF or the important work IVCF does, rather it is an invitation for unity in diversity--something many of us have learned through the embodied credibility of IVCF."

The full draft of the letter is posted below this article with instructions for how other InterVarsity authors can add their names.

These influential authors are not alone in their dismay over IVCF's policy. This week, a public protest letter from "concerned ICVF alumni" was posted on Change.org and addressed to Tom Lin and IVCF's board of trustees. Similar to the authors' letter, this petition stated that signers "hold a range of beliefs with regard to marriage and human sexuality." The petition, in part, states:

The new policy, which excludes many Christian siblings and silences sincere disagreement, contradicts InterVarsity’s values of authentic community, loving-kindness, intellectual rigor, and abundant grace. If not changed, we fear for the future of the organization and its ability to continue to minister to students and faculty, to the ultimate detriment of the gospel message and the legacy of an organization we dearly love.

Today, the petition has exceeded its goal of 1,000 signatures from IVCF alumni.

In addition to these efforts, a large coalition of LGBT Christians has issued a public statement opposing the position. The Gay Christian Network, which has more than 30,000 registered members and runs the world's largest annual gathering of LGBT Christians, sent Religion News Service a draft of a public letter stating concern that "this decision sends a clear message to LGBT students that they are not wanted in InterVarsity--and many will surmise that they are not wanted in the church, either."

The letter asserts, "While we sympathize with the need for religious organizations to be able to take theological positions, we do not believe witch hunts based on privately held personal beliefs are the right way to handle a sensitive issue where many Christians are evolving and where those most affected are a minority community with a history of feeling unwanted in the church."

The full draft of the letter was sent to Religion News Service by Justin Lee, president of the Gay Christian Network and author of Torn: Rescuing the Gospel from the Gays-vs-Christians Debate. It has been posted on the GCN website.

When Elizabeth Dias of Time first broke the story about InterVarsity's policy, the organization responded by claiming that the article incorrectly reported their position. "The scope of InterVarsity’s reiteration of its position on biblical sexuality is primarily theological in nature," a public statement said. In other words, IVCF employees will only be fired for holding to theological positions affirming gay marriage, rather than political positions affirming civil marriage for LGBT persons.

An email attempt to contact Tom Lin was not immediately returned for comment.

*If you are an IVP author/contributor and would like your name added to this letter please indicate that by sending a message here. Also, please note that organizations and titles listed for identification purposes only and do not necessarily reflect the position of the institution.