MSNBC's Martin Bashir (YouTube)

US MSNBC television host Martin Bashir has caused a stir by claiming that Republicans criticising Barack Obama over the Internal Revenue Service (IRS) scandal are actually using the issue as racial dog whistle against the President.

Republicans blame Obama over the tax agency targeting of conservative groups ahead of the 2012 presidential elections "despite the complete lack of any evidence," British born Bashir, 50, told his audience.

"The IRS is being used in exactly the same way as they [Republicans] tried to use the president's birth certificate," the anchor man said referring to the right-wing theory according to which Obama was born in Kenya and therefore not qualified to be president of the United States.

"Republicans are using it [IRS] as their latest weapon in the war against the black man in the White House."

Bashir cited late Republican political consultant Lee Atwater, who in 1981 infamously theorised how Republicans could have conveyed racists' votes while remaining on politically correct grounds.

"You start out in 1954 by saying, 'N*****, n*****, n*****,'" Atwater said. "By 1968 you can't say 'n*****'- that hurts you, backfires. So you say stuff like, uh, forced busing, states' rights, and all that stuff, and you're getting so abstract.

"Now, you're talking about cutting taxes, and all these things you're talking about are totally economic things and a byproduct of them is, blacks get hurt worse than white... "We want to cut this," is much more abstract than even the busing thing, uh, and a hell of a lot more abstract than "N*****, n*****," Atwater said.

"This afternoon, we welcome the latest phrase in the lexicon of Republican attacks on the president: IRS," Bashir concluded. "Three letters that sound so innocent, but we know what you mean."

Bashir's remarks came days after the chairman of a House of Representatives committee investigating the IRS was the last in a long series of Republican figures to link the tax agents' inappropriate behaviour to the White House.

Republican Rep. Darrell Issa, said interviews with tax agency employees indicated that they were directed by Washington to single out for extra scrutiny tax-exempt status applications made by Republican-linked groups.

"This is a problem that was coordinated in all likelihood right out of Washington headquarters and we're getting to proving it," Issa said.

Issa's claim was dismissed by democrats. "Rather than lobbing unsubstantiated conclusions on national television for political reasons, we need to work in a bipartisan way to follow the facts where they lead," Rep. Elijah Cummings said.

Obama condemned IRS malpractice and maintained that he learned about it from the news although Treasury investigators were looking into the matter in April.