The Colorado Senate on Monday gave final approval to a civil unions bill following an initial nod on Friday.

The measure seeks to recognize gay and lesbian couples with civil unions in a state where marriage is not an option due to its 2006 voter-approved constitutional amendment limiting marriage to heterosexual couples.

Without debate, the chamber voted in favor of the measure 21-14, with one Republican, Senator Ellen Roberts of Durango, joining all Democrats.

It is the second year in a row the Senate has approved Democratic Senator Pat Steadman's civil unions bill. Last year's bill died in the GOP-controlled House.

However, after two failed attempts in the House, passage appears to be a foregone conclusion now that Democrats control both chambers.

Christian conservative groups which oppose the measure, such as the Alliance Defending Freedom and CitizenLink, the political arm of Focus on the Family, have previously said that the measure threatens religious freedom.

If the bill is approved, Colorado would join 5 other states – Delaware, Illinois, New Jersey, Rhode Island and Hawaii – which offer the union. However, all 5 of those states, along with Minnesota, are expected to consider legalizing gay marriage this year.

(Related: Hawaii House committee says it won't hear gay marriage bill.)