A new report by Treasury Inspector General for Tax Administration (TIGTA) has identified as many as 146 cases in which the Internal Revenue Service may have put liberal-leaning groups under heightened scrutiny, The Washington Post reported.

The report examined cases between 2004 and 2013. A similar earlier report by TIGTA from 2013 said the IRS had singled-out conservative-leaning groups, sparking accusations from Republicans that the Obama administration had improperly targeted political opponents.

The 2013 report examined cases around the same time period. The new TIGTA report is set to be released Thursday. The Post reviewed an advance copy of the report.

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The new report identified 146 cases of left-leaning groups being targeted for additional scrutiny because of suspicions that they were engaging in prohibited political activity.

Eighty-three of those groups were chosen because of the IRS's selection criteria, which included groups referencing terms like "Occupy," "Medical Marijuana" and "Progressive," as well as any affiliation with the Association of Community Organizations for Reform Now (ACORN).

Groups that were targeted for more intense scrutiny were subjected to long waiting times and arduous requests for information about their donors and political activities, the Post reported.

The report says that it was "inappropriate" for the IRS to single out groups based on their names, rather than on actual evidence of inappropriate activity, according to the Post.

TIGTA's 2013 report identifying 96 conservative groups that were subjected to increased scrutiny by the IRS sparked outrage among some Republicans and prompted the resignations or retirements of top IRS officials.