(Reuters) - Congressional Republicans criticized the U.S. Internal Revenue Service on Tuesday over its loss of emails possibly linked to last year's controversy about the tax agency's treatment of Tea Party-aligned political groups.

Hammering away at the White House and the IRS over the 2013 affair, a handful of Republicans accused the Obama administration of obstructing congressional probes and renewed calls for the naming of an independent prosecutor.

"This entire investigation has been slow-walked by the (Obama) administration," Republican Representatives Dave Camp and Charles Boustany said in a joint statement.

"It looks like the American people were lied to," they said.

White House spokesman Josh Earnest told reporters aboard Air Force One on Monday that the IRS' blaming of a computer crash for the loss of the emails was "entirely reasonable because it's the truth and it's a fact."

He said, "Speculation otherwise I think is indicative of the kinds of conspiracies that are propagated around this story."

The IRS had no immediate comment.

In May 2013, a senior IRS official, Lois Lerner, issued an unexpected public apology for what she called "inappropriate" scrutiny by the IRS of non-profit conservative political groups, triggering Republican outrage.

As part of its duties, the IRS reviews the activities of non-profits that apply for tax-exempt status because U.S. law limits the political involvement of such groups. Non-profits have increasingly been used as conduits for political spending across the ideological spectrum, especially by conservatives.

In the uproar following Lerner's apology, numerous congressional committees held hearings. The acting chief of the IRS stepped down. Lerner, who had headed the IRS' tax exempt division, became a lightning rod for criticism and retired in September 2013. She has said she did nothing wrong.

COMPUTER CRASH

On Friday, the IRS informed lawmakers that it could not produce some of Lerner's emails from 2009 to 2011 because they were wiped out in a computer hard drive crash.

Earnest said the Obama administration has given congressional investigators 67,000 emails either sent by or received by Lerner. He said the IRS has made "a good-faith effort" to cooperate with Congress.

He added that "the far-fetched skepticism expressed by some Republican members of Congress, I think, is not at all surprising and not particularly believable."

In the Senate, the finance committee's top Democrat and top Republican met with IRS Commissioner John Koskinen on Monday to discuss the lost emails. "I was greatly disturbed by what I heard," Republican Senator Orrin Hatch said on Tuesday.

Because of the lost emails, Senator Ron Wyden, the Democratic chairman of the committee, is reassessing when to publish a bipartisan committee report on the IRS' alleged targeting, a committee spokeswoman said on Tuesday.

Koskinen is scheduled to testify next week about the lost emails before two Republican-controlled House committees.

Also on Tuesday, House Republicans proposed cutting the IRS' 2015 budget by 3 percent and blocking an IRS attempt to rewrite its rules for non-profit groups.