(CNN) An IRS employee who is raising concerns about potential political interference in the presidential audit program is declining to voluntarily appear for a transcribed interview with the Senate Finance Committee, according to a source familiar with discussions.

After raising concerns over the summer, the whistleblower met in November with Republican and Democratic staffers on the committee but has declined an invitation to appear for a follow-up, according to the person familiar.

This same person said the whistleblower declined the transcribed interview after an official informed the whistleblower that it could be considered a violation of IRS code to provide the committee with any information related to an individual taxpayer. Under IRS code 6103, IRS employees can be fired, fined or even jailed for disclosing taxpayer information.

It is unclear what next step the committee will take. One option would be to issue a subpoena, but it is not clear that is the route the committee would take.

The Treasury Department did not immediately respond to request for comment.

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