Washington (CNN) -- A group of conservative activists slammed the Obama administration Monday for allegedly planning to use its administrative authority to undercut immigration restrictions in the wake of congressional inaction on a comprehensive reform bill.
In a letter sent to the White House, leaders of 17 conservative grass-roots organizations cited reports that the administration is considering using its executive power "to effectively legalize significant numbers of illegal aliens."
"We strongly urge that you refrain pursuing that tactic," they wrote. "We believe that such an abuse of power would further polarize the immigration issue, which already is so controversial that reasonable discussion is confounded."
Only Congress, they argued, "possesses plenary power over making our immigration policy. The administrative branch has limited discretion for dealing with aliens and quite limited policymaking authority."
The letter, which also cites "abuses of the legislative process" during the health care debate, was signed by members of the Eagle Forum, Judicial Watch, the Family Research Council and a Washington-area segment of the Tea Party movement, among others.
The White House has "come up with a back door plan to bypass the Congress and the American people," Colin Hanna, head of the group Let Freedom Ring, said at a news conference Monday.
"The administration is terrified that the illegal immigrant population is going to go down further because they want to keep them here in order to give them the amnesty and turn them into voters," alleged Roy Beck, head of NumbersUSA, which favors tighter immigration restrictions.
At issue is an internal Department of Homeland Security memo outlining multiple options for assisting illegal immigrants in the absence of new legislation.
The 11-page document, titled "Administrative Alternatives to Comprehensive Immigration Reform," describes how to reduce the threat of removal for some undocumented immigrants through various administrative and regulatory changes. It characterizes one potential change as "a non-legislative version of amnesty."
Among other things, the document describes a draft proposal to "extend benefits and/or protections" to individuals currently "present in the United States without authorization."
It also mentions the possibility of "deferred action," defined as "an exercise of prosecutorial discretion."
The document, initially obtained by GOP Sen. Charles Grassley of Iowa, indicates the suggestions have the "potential to result in meaningful immigration reform" without congressional action. It acknowledges, however, a broad price tag if the ideas are adopted without restraint.
"While it is theoretically possible to grant deferred action to an unrestricted number of unlawfully present individuals, doing so would likely be controversial, not to mention expensive," the document says.
Representatives of U.S. Citizenship and Immigration Services -- the Homeland Security agency responsible for drafting the memo -- indicated in a statement last month that the document was merely brainstorming.
"Internal memos do not and should not be equated with official action or policy," the statement noted. The Homeland Security Department "will not grant deferred action or humanitarian parole to the nation's entire illegal immigrant population."
CNN's Alan Silverleib contributed to this report