(Updates with quotes from McConnell and Obama, background)
By Thomas Ferraro
WASHINGTON, May 14 (Reuters) - U.S. Senate Republican leader Mitch McConnell called on President Barack Obama on Tuesday to make available for questioning everyone who knew about the Internal Revenue Service's targeting of conservative groups, and demanded "no more stonewalling."
With Congress preparing to hold hearings on the IRS's holding conservative groups to extra scrutiny, McConnell said he was "calling on the president to make available, completely and without restriction, everyone who can answer the questions we have as to what was going on at the IRS, who knew about it, and how high it went."
"No more stonewalling, no more incomplete answers, no more misleading responses, no holding back witnesses, no matter how senior their current or former positions - we need full transparency and cooperation," McConnell, of Kentucky, said on the Senate floor.
The scandal was ignited on Friday when an IRS official revealed at a meeting of tax lawyers that the agency had inappropriately singled out Tea Party movement and other conservative groups for extra examination of their claims for tax-exempt status.
Obama on Monday said the IRS's targeting of the Tea Party and other conservative groups for additional tax scrutiny was outrageous and that any IRS employee involved would be held accountable.
But Obama's words failed to ease the ire of Republicans in Congress and conservative groups, who question how far the IRS went and who set the policy.
Republicans as well as Obama's fellow Democrats promise congressional hearings that are expected to sap energy from Obama's legislative agenda, including his push to overhaul the nation's immigration system.
Citing media reports, McConnell said, "targeting wasn't limited to an IRS office out in Cincinnati - as the administration suggested last week - but that it reached all the way to IRS headquarters in Washington."
"What we don't know at this point is whether it jumped the fence from the IRS to the White House," the Senate Republican leader said.
"But we do know this: we can't count on the administration to be forthcoming about the details of this scandal - because so far they've been anything but."
The targeting began in 2010, shortly after the emergence of the conservative Tea Party movement, which helped Republicans, in the election that year, pick up seats in the Senate and control of the House of Representatives.
(Reporting by Thomas Ferraro; Editing by Vicki Allen)