Job applicants might not want to wear their religion on their sleeves. At least that’s the message that could be taken from a growing number of studies that show religious discrimination often plays a significant role in the hiring process.

In the most extensive studies to date, researchers found that otherwise identical fictitious resumes listing membership in student religious organizations received fewer responses from US employers than those with no mention of religion. The prejudice was stronger in southern states than in New England states, where there is greater diversity of religions and people tend to be more tolerant of other faiths.

“There has been a privatisation of religion,” said Michael Wallace, a sociology professor at the University of Connecticut and co-author of the recently published studies. “We’re perfectly willing to acknowledge the right to religious freedom, but we prefer that religion not be present in public places like schools or workplaces, where there will likely be people with diverse religious beliefs.”

Employers may harbour personal prejudices against certain faiths. They also could fear that people who decide to reveal their religious beliefs — or their atheism — on resumes are more likely to discuss religion and potentially clash with co-workers.

“The religious aspect of the resume may jump out to recruiters and raise the questions of whether such people will disrespect others with a different religious identity — or no religious beliefs at all,” Wallace said.

Religious affiliation, however, could work in an applicant’s favor in some cases. In the study of southern states, Jews actually seemed to have an edge over other applicants. What’s more, religious organizations in the US are allowed to give employment preference to members of their own faith.

But business owners who apply their personal religious beliefs to their companies’ policies would rarely be allowed to show hiring preference to people of their own faith. The exception would be when religion “is a bona fide occupational qualification reasonably necessary [for the company’s] normal operation,” according to the US Equal Employment Opportunity Commission.

That means Hobby Lobby, which the US Supreme Court recently ruled could deny insurance coverage for some female contraceptives because of its owners’ Christian beliefs, probably couldn’t favour Christians in its recruiting. The company runs a chain of arts and crafts stores, where an employee’s religious beliefs would be unlikely to affect business operations. However, companies like Hobby Lobby might try to use their religious beliefs to justify discrimination against gay, lesbian and transgender job candidates.

Studies in France and Greece have found hiring bias for certain religious groups. The French research revealed that a Muslim with African heritage was two-and-a-half times less likely to get called for a job interview in France than an equally qualified Christian with the same ethnic background.

“We find a good deal of evidence that [people] in Christian heritage societies, although themselves secular — and many of them self-declared atheists — see Muslims as presenting a set of cultural norms that are threatening to them,” said David Laitin, a political science professor at Stanford University and one of the authors of the study.

In the Greek study, fictitious applications were sent to employers to gauge reactions to the majority Greek Orthodox faith and three minority religions. Compared to the Greek Orthodox applicants, the job seekers who were identified as Pentecostal, Evangelical or Jehovah’s Witnesses had less access to job interviews and received lower entry-level wages. What’s more, they also were less likely to be chosen for more prestigious jobs, according to Nick Drydakis, who conducted the research and is a senior lecturer in economics at Anglia Ruskin University in the UK.

Comparatively, a US study found that in New England, Muslim applicants were shunned the most, receiving one-third fewer responses from employers than those who listed no religious affiliation. There was also evidence of discrimination against atheists, Roman Catholics and pagans.

In southern states, where the dominant religion is Christianity, Muslims, pagans and atheists were targets of the most prejudice, followed by Roman Catholics. Even evangelical Christians experienced a little discrimination based on the number of applicants contacted by employers compared with those whose resumes were entirely secular.

In addition to resume information, religious content on social-media sites also could be problematic. Recruiters these days routinely check applicants’ social-networking activity and could screen out members of religious denominations or atheists.

“There’s a belief that people come to work and leave religion at the office door — and that they should,” said Joyce Dubensky, CEO of the Tanenbaum Center for Interreligious Understanding in New York City. “The truth is, that just doesn’t happen. Religion is an important way in which people define themselves and employers need to learn how to manage people of different religions as the workplace becomes more and more diverse.”

The center surveyed American workers last year and found that not only do members of religious minorities and atheists feel “marginalized” by employers, but that the Christian majority also considers discrimination a serious issue.

Employees usually have little doubt when they experience religious discrimination in the workplace. But job candidates rarely ever learn that religious information on their resumes or social media sites took them out of the running.

If applicants get to the interview stage, however, religious bias may become more overt. The EEOC has received a number of complaints from job candidates charging employers with religious discrimination during interviews. Overall, the annual number of EEOC religious discrimination cases, including those from both applicants and employees, has nearly doubled since 9/11, peaking at 4,151 in 2011.

Muslims particularly encounter bias. Clothing retailer Abercrombie & Fitch, for example, agreed to pay $71,000 last year to settle two separate religious discrimination lawsuits brought by the EEOC on behalf of Muslim teenagers whose hijabs conflicted with the company’s “Look Policy” dress code. In one case, the EEOC lawsuit alleged that Halla Banafa was asked about her headscarf and religion during her interview and then denied a job at one of Abercrombie’s California stores. A federal judge dismissed the company’s undue hardship defense, citing the lack of proof linking store performance or brand image to “Look Policy” compliance.

In recent years, the EEOC also has won cases involving a Sikh who failed to land a Lexus car dealership sales position because he wouldn’t shave his beard; a Rastafarian who wasn’t hired by a moving and storage company because he wore his hair in dreadlocks; a female fundamental Baptist who refused to wear trousers and was rejected for a staffing agency job; and several people, including a Jew and Seventh-day Adventist, who didn’t get jobs because they wouldn’t work on their Sabbath.

Employers often fear that visible signs of religious affiliation, such as hijabs or crosses, will offend customers or clients. “But customer preference is not a defense” in a religious discrimination case, said Jeanne Goldberg, senior attorney advisor at the EEOC.

She believes “the 24/7 economy” has contributed to more religious bias because many employers want to avoid hiring people who will ask for scheduling accommodations to attend religious services.

Religious discrimination is especially problematic for students and recent graduates with little work experience who may want to show their potential by including leadership positions in campus religious groups on their resumes.

“It’s a troubling phenomenon that people have to consider hiding their religion, but it’s something that you have to think about if you want to get the job,” Dubensky said. On the other hand, some candidates may want to reveal their religious identity to steer clear of discriminatory employers.

“I know a star candidate who received a management job offer from a global financial services company,” Dubensky said. “But she went to a competitor that was known to be more hijab-friendly.”

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