Treasury Secretary Donald T. Regan criticized a story in yesterday's Washington Post about proposals to phase out the income tax deduction for state and local taxes and taxing unemployment compensation and workman's compensation.

"It is absolutely untrue that we have made any final decision," he said. "It's a shame to have uninformed and inaccurate conjectures that arouse unjustified anxieties." The story said that Regan had tentatively approved the tax changes.

Regan said he expected more of what he characterized as "false reports" to be circulated about the Treasury's tax reform study. The study, called for by President Reagan in his State of the Union address last January, is expected to be complete sometime in December. Regan said any interim reports about what the study might recommend should be treated as "idle speculation."

President Reagan declined to comment on any specifics that might be in the report until he receives it from Treasury, but House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) was quick to react.

"Unemployment is a personal tragedy," he said. "To add full taxation to the burden of joblessness is extremely unfair, even by this administration's standards. Only a Scrooge would hit a worker when he is down."