Citing an inability to support a proposed $800 million tax package, the chair of the Massachusetts House Post Audit and Oversight Committee resigned yesterday morning.

Robert A. Cerasoli (D-Quincy) said that House Speaker George Keverian '53--who came up with the tax plan aimed at closing the estimated $720 million state budget deficit--pressured him to step down from the post if he did not plan to vote for the bill.

"He implied that he wanted my resignation if I wasn't with him," Cerasoli said.

Keverian has asked most members of the House leadership to back the tax package, and an aide to Cerasoli said other committee chairs who oppose the increases might resign as well.

"[Cerasoli] thought it would be unfortunate to have the speaker judged simply on the fact that he could not persuade his chair to vote with him on the tax increase," said the aide. "He has set a standard that a number of others are going to have to consider."

But Rep. Joseph N. Hermann (D-North Andover), chair of the State Administration Committee, said the speaker did not ask him to step down if he chose not to vote for the tax hike, but said he would resign to preserve House leadership unity, if necessary.

Other representatives said their opposition to the bill would not break down the House leadership.

"It will show a difference of opinion" among the leaders and nothing else, said Rep. John C. McNeil (D-Malden), who declined to comment on how he would vote.

The details of the tax package, expected to be reported out of the House Ways and Means Committee today and debated on the floor tomorrow, are still being worked out between Keverian, House Majority Leader Charles F. Flaherty (D-Cambridge) and the House Ways and Means staff, said committee member Joseph K. Mackey '74 (D-Somerville).

Mackey said that, as of last night the package calls for the sales tax to increasefrom 5 to 7 percent, the capital gains tax to risefrom 5 to 7.5 percent, a "sin" tax on alcohol andtobacco to go up and this year's gasoline tax tosuffer a six-cent increase, followed by a two-centincrease for the next two years.

Passage Questioned

But several House members said they do notthink Keverian has the 81 votes needed to win thebill House approval.

"I don't think they have enough votes for it,and I think they're losing votes as it drags on,"said Rep. Barbara E. Gray (R-Framingham), who,like many of her Republican colleagues, opposes atax increase until further cuts in the budget aremade.

And a legislative aide to 1990 gubernatorialcandidate Steven D. Pierce (R-Westfield) saidPierce believes current deficit predictions aretoo gloomy. He added that for this reason, furtherbudget cuts and the deficit reduction bill passedby the House two weeks ago--which will beconsidered in the Senate later this week--shouldcover the shortfall