House Ways & Means Committee Chairman Dave Camp (R-Mich.) on Wednesday accused the Obama administration of preventing an official with information about the IRS scandal from testifying until after the November election.

Camp wrote to Treasury Secretary Jacob Lew to point out that his committee asked in mid-September to hear testimony from Hannah Stott-Bumstead, a lawyer who may have been the first person told about the lost emails of former IRS official Lois Lerner.

Congress is still asking questions about the scandal involving Lois Lerner and the IRS, run by Commissioner John Koskinen, but the Treasury Department is delaying the availability of a key witness. Chip Somodevilla/Getty Images

Camp said that while he had hoped to hear from the witness within two weeks, and Treasury seemed to have no objections to having her testify, Treasury later ignored their request.

"Treasury officials ignored this committee's phone and email inquiries about Ms. Stott-Bumstead's availability," Camp wrote. "On the morning of October 14, a month from the initial request, the same Treasury officials told staff that Ms. Stott-Bumstead was not available until sometime in November."

Camp also said he was told by Treasury that interviewing a Treasury lawyer poses "Constitutional and practical concerns." But Camp said the committee has interviewed more than a dozen Treasury lawyers already.

"Why the sudden change in protocol?" he asked.

Read his letter here: