Rep. Al Ullman (D-Ore.) is coming under intense criticism for his handling of the pending tax bill, with the possibility that it could jeopardize his post as chairman of the House Ways and Means Committee if the tax measure goes further awry.

Last weekend, after Ways and Means had approved a $16 billion tax cut, a few committee liberals openly called for deposing Ullman as chairman. Since then their anger has faded somewhat, but Ullman clearly has aroused disappointment both among members of the House leadership and among younger, more liberal Democratic House members.

One respected liberal speculated yesterday that the junior members might try to challenge Ullman's seat as chairman at the start of the next congressional session next January, and predicted that there could be "as many as 100 votes against him."

In addition, several sources confirmed that House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) was so enraged by the Ways and Means effort on the topic bill that he called Ullman in earlier this week and "chewed him out up and down." Ullman was reported to have promised to do anything O'Neill wanted on the bill, the sources said.

A source close to the leadership suggested that Ullman's fate as committee chairman could hinge in part on how the tax bill fares on the House floor next week. If the bill is "mismanaged" and the GOP scores a major victory, he said, "then anything is possible."

The grumbling about Ullman's performance has centered on two complaints.

First, critics says, Ullman "failed to exercise strong leadership" on the tax bill, effectively allowing Republicans to dictate the contents of the measure. "He never got the Democrats together," one critic said. "And he gave away a lot more than he needed to."

The bill Ways and Means approved last week bears almost no resemblance to President Carter's tax proposal - particularly on the issue of reductions in capital gains taxes. A breakdown of the benefits shows that large portions would go to high-income taxpayers.

Second, say critics, Ullman needlessly handed the panel's Republicans a key victory by promising them a separate floor vote on the GOP-sponsored Kemp-Roth tax-cut proposal in return for their support of the committee bill. Many junior members are reluctant to face a vote on Kemp-Roth.

Many House liberals say they are disgusted with Ullman's performance - particularly on capital gains taxes, which are applied to the profits from the sale of stocks or other assets. Rep. Charles A. Vanik (D-Ohio) termed the bill "a terrible mistake."

Even administration officials have been openly critical of the chairman. Several key officials are known to feel that the administration was sand-bagged when Ullman agreed to work with Republicans on a "compromise" capital gains measure.

Defenders of the chairman point out that in today's emotion-filled political climate, managing the tax bill in the committee is an especially touchy operation. The administration was ineffective in its lobbying, the panel's liberals were in disarray, and conservatives controlled the votes.

Moreover, Ullman allies argue that he too often is being compared unfairly with his predecessor, former representative Wilbur D. Mills (D-Ark.), who had what some say was an exaggerated reputation as a shrewd manager. Mills worked under a system that afforded him more power.

Ullman was not available for comment yesterday. But a source close to the chairman said he believed the initial round of complaining "has died down now," and that the flap essentially was over. And another insider said O'Neill, too, had gotten over his earlier ire.

Two factors appear to be cooling the move toward any formal challenge to Ullman's post right now: first, despite the griping by some junior Democrats, the liberals don't have enough support to win a majority in caucus, and second, they don't have a candidate to succeed him.