President Carter's embattled welfare bill appeared in deep, possibly fatal trouble yesterday as a special House welfare subcommittee met in an atmosphere of gloom to continue work on it.

Despite reports that House Speaker Thomas P. (Tip) O'Neill (D-Mass.) is considering an end run to speed up action, key subcommittee members said they doubt there will be time for the Senate to pass the bill this session even if it gets through the House soon.

One predicted it won't come up in the Senate at all. Another said it will be torn to pieces in the House.

House Ways and Means Committee Chairman Al Ullman (D-Ore.) and Augustus F. Hawkins (D-Calif.), chairman of the House Labor employment opportunities subcommittee, said there is no chance their committees - let alone the full House - can complete work on the bill by the April 1 target date set by James S. Corman (D-Calif.), the bill's sponsor.

Corman has said the bill should be passed by the House and sent to the Senate by that date so Senate backers can have time to overcome massive resistance by such opponents as Senate Finance Committee Chairman Russell B. Long (D-La.)

Yesterday, as Corman called the special welfare subcommittee into session, Hawkins said flatly it is "unlikely" the target date can be met. Hawkins said his subcommittee will not finish work on the public service employment sections of the bill until the middle or end of April, and he wants to act first on various other jobs and training measures.

Then he added in an interview, "He's being unrealistic on a bill that isn't going anywhere this year. Obviously the Senate isn't going to vote on it this year."

Rep. Barber Conable (R-N.Y.), who happened to be walking by at that moment, said, "'Why bother?' is a very good question."

Ullman, meanwhile, announced that the full Ways and Means Committee would be occupied with the president's tax proposals throughout March and couldn't begin to look at the welfare bill before April 1, let along send it to the floor by then.

Another influential and important member of the subcommittee, asking not to be identified, said, "If this bill passes the House in any form like the president asked this year, I'll buy you a three-martini lunch."

Corman, however, said he's going to press forward and do the best he can.

If the bill doesn't reach the Senate early this spring, it is considered a sitting duck for stalling tactics that would prevent a floor vote this year.

Conservative critics believe the bill's increases in welfare benefit levels, high-level pay for proposed "last-resort" public service jobs ($9,600 or more) and massive costs (at least $20 billion more than the present program, according to some estimates) will induce people to seek welfare rather than private jobs and will bankrupt the country.

The speedup action being considered by O'Neill would, in effect, set a time deadline sometime in late spring for the bill to go to the floor, whether work had been completed by the Ways and Means, Labor and Agriculture committees.

Once on the floor, amendments to restore the measure to whatever form is worked out by Corman's subcommittee would be in order. The deadline wouldn't be April 1, but it could be the end of April or in May.

Last week in an interview with The Washington Post, high but unnamed White House officials said they had concluded the same thing Hawkins openly (and other special subcommittee members privately) said yesterday the bill can't pass the Senate this year and might as well be put on a back burner.

These officials, as well as the president himself, publicly denied it the next day, but there is a deepening belief in the special Corman subcommittee that the White House has indeed come to that conclusion and is relexing its efforts to speed the bill.

Some liberal groups and unions, which had been expected to support the bill, are critical and may yet oppose it altogether because they consider benefit levels too low in some cases.

Some unions consider the pay levels for public service jobs of $9,600 a year or more barely adequate to match the normal prevailing wages in some areas. Unless they do match, they argue, the bill could create a pool of cheaply paid "welfare laborers" who could be used to replace higher-paid union workers.

Labor spokesmen were furious yesterday when a proposal to raise the proposed welfare benefit amount paid to a family with an able-bodied worker, if he or she were unemployed, was defeated, 15 to 13.

With the "Natural constituency" of labor and welfare groups battling among themselves over how high to raise benefits, and with the April 1 deadline slipping away, the bill's prospects look increasingly bleak.