(CNN) -- The number of radical right groups in America -- including hate groups, "Patriot" groups and nativist groups -- increased in 2010 for the second year in a row, according to a report by the Southern Poverty Law Center.
The organization's quarterly publication, Intelligence Report, said the growth was "driven by resentment over the changing racial demographics of the country, frustration over the government's handling of the economy, and the mainstreaming of conspiracy theories and other demonizing propaganda aimed at various minorities."
The SPLC documented 1,002 hate groups operating in the United States in 2010, a 7.5% increase from the year before. It was the first time that more than 1,000 hate groups were recorded since the organization started tracking them in the 1980s.
But the biggest growth was in so-called "Patriot" groups, which the organization described as conspiracy-minded groups that see the federal government as their primary enemy. There were 300 new groups like this, an increase of more than 60% from the year before, the report said. A lot of the growth in the Patriot groups came from an increase in the number of militias recorded.
There was also a smaller increase in the number of anti-immigrant vigilante groups, SPLC reported.
"We were expecting to see the winds out of their sails because of the mainstreaming (of some of the radical right's ideas), but that hasn't been the case," said Mark Potok, director of SPLC's Intelligence Project.
He cited developments in the past year such as the passing in Arizona of a restrictive immigration law as an example of extremist ideas being folded into the mainstream.
Politicians affiliated with the Tea Party movement have also co-opted some of the extremist groups' agenda, ranging from attacking birthright citizenship to requiring special permission for federal agents to carry out operations without the local sheriff's consent.
But, Potok pointed out, there is a difference between the Tea Party movement and the Patriot movement described in the report.
The Tea Party is not considered an extremist or hate group, "but there are some strains of extremism" in it, he said.
On the organization's website, there is a new map that includes a list of all the hate groups and extremist organizations operating in each state. The rise of the Patriot groups is especially notable because this is the subset of radical right groups most associated with violence.
"The real large criminal plots have come more from Patriot groups than the hate groups," Potok said.
As an example, he noted a man with a long history of anti-government activities who was arrested in January in a car filled with explosives outisde a mosque in Dearborn, Michigan.
There was also a case of a neo-Nazi who was arrested in January as he headed for the Arizona border with a dozen homemade grenades, and another case where police discovered a plot to bomb a Martin Luther King Jr. Day parade in Spokane, Washington, he said.