US justice authorities said Tuesday they had launched a criminal probe into the Internal Revenue Service's targeting of conservative, as the White House denied involvement in the scandal.

Attorney General Eric Holder said he had ordered an investigation into the federal tax authority's treatment of Tea Party non-profit groups, to see if it had violated any criminal laws.

"The FBI is coordinating with the justice department to see if any laws were broken in connection with those matters related to the IRS," Holder told reporters.

"Those were, I think, as everyone can agree, if not criminal, they were certainly outrageous and unacceptable," Holder said.

"But we are examining the facts to see if there were criminal violations."

The White House meanwhile denied any ties to the IRS action which, coming together with two other fresh scandals, have put President Barack Obama's administration in a tight squeeze just months into his second term.

Pressed by reporters to confirm that no member of the White House political or governing team had been involved in the IRS program, Obama's spokesman Jay Carney replied "Yes."

But Carney demurred when asked what action Obama would take on the case, after having said Monday that if true, the IRS actions would be "outrageous".

"We're going to wait and see what the facts are based on the independent inspector general review," Carney said.

On Friday, the IRS admitted targeting around 75 non-profit groups associated with the ultra-conservative Tea Party movement, as well as other political non-profits, for special examination in 2011-2012, as Obama fought a furious battle for reelection against conservatives.

The news triggered triggered a furious response from Republican officials against Obama's administration.

Officials of the IRS, an independent agency within the US Treasury Department, have denied that the probes were partisan.

They involved the claim of non-profit status by newly-formed, so-called 501(c) groups -- many of which were actively involved advocating political stances both sides of the political spectrum.