(Reuters) – The number of extreme anti-government groups in the United States grew to an all-time high in 2012, and a backlash against federal gun control measures could fuel more growth in the movement, the Southern Poverty Law Center said on Tuesday.

Active militia and so-called Patriot groups totaled 1,360 last year, a massive jump from the 149 recorded in 2008 in an annual count of extremist groups by the Alabama-based civil rights organization.

The number of organizations the center terms hate groups, or those that attack minority groups, dropped slightly to 1,007 in 2012 from a record high of 1,018 in 2011.

Active hate groups identified by the center are scattered throughout the country and include the Ku Klux Klan, neo-Nazis, white nationalists and racist skinheads.

Some organizations, such as Christian groups, strongly object to their categorization by the center as “hate groups” and say the civil rights organization is itself stirring up hatred.

In a letter on Tuesday, the center’s president urged Attorney General Eric Holder and Homeland Security Secretary Janet Napolitano to shore up federal resources devoted to countering the threat of domestic hate and extremist groups.

“As in the period before the Oklahoma City bombing, we now also are seeing ominous threats from those who believe that the government is poised to take their guns,” said president J. Richard Cohen on behalf of the law center.

The Patriot movement last reached a peak in 1996, a year after right-wing extremist Timothy McVeigh set off a truck bomb outside the Oklahoma City federal building, killing 168 people. McVeigh and a co-conspirator were convicted. McVeigh was executed.

Homeland Security spokeswoman Nicole Stickel said on Tuesday the department has been working with law enforcement “to better mitigate and respond to violent extremism, regardless of the ideological beliefs that may motivate it, including violence perpetuated by violent sovereign citizens and anti-government militia groups.”

The number of such groups, whose adherents view the federal government as their enemy, dwindled in the late 1990s and early 2000s only to rise sharply in the past four years.

A sluggish U.S. economy combined with the election and re-election of Democrat Barack Obama as the country’s first black president have stoked anger and fear in some Americans and helped drive the growth of extremist groups, said Mark Potok, senior fellow at the center and editor of the report.

GUN CONTROL EFFORTS COULD SPARK NEW GROWTH

Potok said the national conversation about gun control since the December shooting deaths of 20 children and six adults at a Connecticut elementary school could cause the number of anti-government groups to swell again.

Congress is considering bills that would ban assault weapons, expand background checks for prospective gun buyers, crack down on illegal gun trafficking and improve school security.

A number of states are contemplating laws aimed at nullifying any federal gun control measures.

“We are seeing this huge reaction to the potential of gun control,” Potok said. “And that reaction is so angry that it is hard not to be afraid of what is coming down the road.”

Potok said membership totals for U.S. hate and anti-government groups were difficult to ascertain. He estimated there are between 200,000 to 300,000 people involved in hate groups and 300,000 to 400,000 in militia groups.

Among hate groups identified by the center is the Family Research Council, a conservative Christian lobbying group, due to its anti-gay stances. The group strongly rejects its categorization as a hate group and says “reckless rhetoric” from the Southern Poverty Law Center spurred a shooting at its Washington headquarters last summer. The center denies the charge.

“They are the ones who are fomenting hatred against us which has resulted in violence against us,” said Peter Sprigg, senior fellow for policy studies at the Family Research Council. “To label us a hate group is clearly a slander.”

The number of hate groups may also increase in response to immigration reform measures that reinforce their members’ fears about the country’s changing demographics, including the projected loss of the white majority, the law center said in its report.

(Reporting by Colleen Jenkins; Editing by Cynthia Johnston and Andrew Hay)