Catholic leaders in Colorado are rallying against a proposed bill that would recognize gay and lesbian couples with civil unions.

According to the Denver Post, the Colorado Catholic Conference on Sunday handed out fliers calling on parishioners to oppose the bill.

The flier includes a photograph of a heterosexual couple at the altar on one side and a form to be sent to lawmakers on the other.

“I am writing to express my opposition to any civil union legislation,” the form states. “The key flaw with civil union legislation is that it creates an alternative parallel structure to marriage.”

“I believe that traditional marriage is the cornerstone of our society that exists for the benefit of children and the protection of women.”

Last week, Democratic Senator Pat Steadman reintroduced the civil unions bill (Senate Bill 2) that died last year in a Republican-controlled House committee after the Senate approved the measure. Supporters in the House are looking for a Republican co-sponsor before introducing the bill there.

A 2006 voter-approved constitutional amendment that defines marriage as a heterosexual union bars lawmakers from pursuing gay marriage.

The Post noted that it was unclear how many parishes handed out the fliers.

(Related: Bishop James Conley calls Colorado civil unions bill “dangerous.”)