BOSTON (AP) — New Hampshire Sen. Jeanne Shaheen on Wednesday called for a complete and thorough audit of the Internal Revenue Service.

Days after the nation's tax enforcement agency admitted inappropriate scrutiny of conservative groups, the Democrat said that only an audit by the IRS' inspector general would help the IRS regain the "faith and trust of the American people."

Attorney General Eric Holder announced this week that the Justice Department was investigating the agency after it acknowledged agents had singled out conservative groups for extra scrutiny when they applied for tax-exempt status.

Shaheen, who is up for re-election next year, said the scandal raises questions about IRS leadership.

"In light of these abuses, and in the interest of fairness for all taxpayers, we need a full and thorough audit of all of the IRS's practices," Shaheen said in a statement.

The call for an audit comes as the first-term senator faces Republican criticism for previously suggesting that nonprofit groups may be abusing the tax code. She faces her first re-election test in 2014.

Shaheen last year joined several Democrat senators, including Sen. Chuck Schumer, D-NY, and Sen. Sheldon Whitehouse, D-RI, in a letter asking the IRS to crack down on nonprofit organizations that were "engaged in a substantial amount of political campaign activity."

The lawmakers did not identify any conservative groups in the March 2012 letter.

Four months later while debating a separate bill, Shaheen took a more partisan approach while publicly criticizing groups that take advantage of the tax code to offer keep secret their donors' identities. In a July speech on the Senate floor, the senator singled out the tea party ally, Americans for Prosperity, as an example.

New Hampshire GOP executive director Matt Slater on Wednesday questioned whether Shaheen's past comments helped contribute "to the outrageous practices that took place" at the IRS.

"Shaheen and her Democrat colleagues have consistently attacked conservative organizations, but said nothing about the liberal social welfare groups that have supported their campaigns," Slater said.

Shaheen said the scandal could have been avoided had the agency heeded her recommendation.