Conservative Christian organizations are rallying to urge Congress to end the federal income tax "penalty" that wedded pairs have paid for three decades.

A bill introduced by Rep. Jerry Weller (R-Ill.) and Rep. David McIntosh (R-Ind.) would eliminate the surcharge working married couples pay on their taxable income. A similar measure has been introduced in the Senate, while Democrats have proposed a less-sweeping version.

The tax code imposes an average $1,400 surcharge on the dual incomes of a married couple, versus what the two would pay if they filed as single adults. "Not only is the marriage penalty unfair, it's immoral that our tax code punishes society's most basic institution," Weller said in a GOP radio address.

The Christian Coalition has made eliminating the marriage tax penalty its top tax priority this year. "If Congress is unwilling to scrap the (IRS) code, then elimination of the marriage tax penalty should be of the highest priority in order to encourage marriage and ease the burden on families trying to form and stay together," the Christian Coalition said in a statement.

Concerned Women for America has also been lobbying. "Marriage is the foundation of our society, and any policy that weakens that foundation hurts our country," says CWA founder Beverly LaHaye.