The Illinois Department of Human Rights is investigating one of the largest corporations in the country for alleged sexual orientation discrimination.

Freedom to Work brought the discrimination charges against Exxon Mobil earlier this month. The national organization works against sexual orientation discrimination in the workplace and says Exxon is the single worst offender of LGBT discrimination in the country.

The organization says it sent nearly identical resumes to Exxon. But one applicant had a higher GPA, longer work history, and volunteered with a gay organization in college. That applicant allegedly never got an interview, while the other applicant did.

Tico Almeida is the organization’s founder. He says they did the discrimination test in dozens of states, but brought charges in Illinois because it has some of the strongest sexual orientation protections in the country. It outlawed sexual orientation discrimination in 2006 while Texas, where the organization also found evidence of discrimination, has no such law.

“Exxon could actually put out a sign on their door in Texas that says gays not apply and that would be perfectly legal,” Almeida said.

Freedom to Work hopes the case will help them push for federal sexual orientation protections. It’s pressuring President Barrack Obama to sign an executive order banning corporations with discriminatory practices from federal contracts. It is also pushing to pass the Employment Non-Discrimination Act (ENDA), federal legislation that would provide protections against sexual orientation discrimination.

Exxon Mobil says they received the charges and are in the process of evaluating them in the context of their company’s policy.

The Illinois Department of Human Rights started the investigation today and says it will likely take a year.