ATLANTA(CNN) -- Speaking on a conservative talk radio show in Iowa, Colorado Rep. Tom Tancredo announced Monday that he will seek the Republican presidential nomination in 2008.

The outspoken advocate of clamping down on illegal immigration said talk radio has given him a "megaphone" to speak out on the topic. He said that is why he decided to announce his candidacy on Jan Mickelson's "Mickelson in the Morning" show on WHO Radio.

"They're the ones who brought me to the party," Tancredo said, referring to conservative talk radio.

He said he was running because the current GOP candidates are not focused enough on illegal immigration.

The five-term congressman launched a presidential exploratory committee and filed papers with the Federal Election Commission in January.

In a statement on his committee's Web site, Tancredo blamed the GOP's losses in November's congressional elections on what he called its abandonment of core principles such as limited government, public integrity and fiscal discipline.