District of Columbia officials said yesterday that nearly 12,000 youths in Mayor Marion Barry's summer jobs program will have to start work late because the city government has been unable to process the necessary papers and obtain all its project funds on time.

For weeks, city officials have said that the well-publicized jobs program, with a goal of hiring 30,000 youngster, would begin Thursday.

Yesterday, however, Matthew F. Shannon, acting director of the D.C. Department of Labor, indicated to a House committee that only some of about 18,000 youths would be able to start work Thursday. The others would begin work by July 9, he said.

"We started working on summer jobs, I believe, too late," Shannon told the subcommittee.

Later, Shannon told a reporter, "The paperwork has not been processed, parents have not come in and verified income, some [youths] don't have all the information we want, some don't have work permits, some have not been certified. . . . The funds are not coming forth as quickly as possible."

Mattie Taylor, acting deputy director of the department, said about 18,000 youths - including 13,500 persons in special jobs set aside for low-income youngsters - would begin Thursday. Another 2,500 would begin work by July 2, she said.

The remainder should be at work by July 9, and all youths, no matter what time they start, should work the full eight weeks scheduled, she said. "If everything in the program was finished and verified for one opening date, it would be a miracle," Taylor said.

Despite the late starts, the jobs project cleared a second major congressional hurdle yesterday. Rep. Charles Wilson (D-Tex.), chairman of the House District Appropriations Subcommittee, said he would support allocation of $7.3 million requested by Barry to provide 8,600 of the summer jobs.

With Wilson's support and that of Sen. Partrick J. Leahy (D-Vt.), the $7.3 million is expected to be approved by Congress and sent to the White House for President Carter's signature before the end of next week.

Barry, who promised during his campaign to double from 15,000 to 30,000 the number of summer jobs for chronically unexployed city youth, made the summer jobs package the top priority item in a $76.5 million supplimental budget for the current fiscal year.

The Senate Appropriations Committee approved and sent to the Senate on Monday a $53.1 million version of that budget that includes full funding for the summer jobs program.

At yesterday's hearing, Rep. Carl D. Pursell (R-Mich.), ranking minority member of the House subcommittee, said he would try to add to the bill $1.4 million to provide 500 year-round jobs for adults with dependents. The Senate committee provided no money for that project.

More than 40,000 youths that have applied for summer jobs. Only 28,6000 actual job openings have been identified. By the middle of next week, 30,000 slots should be located, Shannon said. As of Tuesday, only 17,652 positions were filled, Taylor said, and another 2,800 should be filled by early next week.

Taylor said the city has been delayed in filling jobs because none of the 8,600 jobs to be paid for through the legislation pending in Congress could be filled until Tuesday, when City Administrator Elijah B. Rogers thought funding was certain.

"Had we known in April that we were definitely going to get the D.C. appropriation, we could have started referring those kids earlier," Taylor said.

Funds for the other 21,400 jobs has already been allocated to the city or will be paid by nongovernmental employers.

Marty Beyer, director of the D.C. Coalition for Youth, was sharply critical yesterday of th city's administration of the summer jobs program and the anticipated delays in youngsters starting work.

"The D.C. Department of Labor has handled it incompetently," she said. "Every step of what they have done is very poorly designed and based on the problems of bureaucrats rather than what the young people need."

She said that the city Labor Department had refused to change its procedures and use methods that could have accelerated the income verification process for low-income youths, and declined to assign students to jobs based on preference and skills. Taylor denied the allegations.

Beyer said the delay in starting was due completely to the city Labor Department's "incompetence."

"The youngsters assumed that there is some inequity there, and kids are also going to be very discouraged on June 28," Beyer said. "Everybody in town is talking about going to work on June 28." CAPTION: Picture 1, MATTHEW F. SHANNON . . . program began too late; Picture 2, At House subcommittee meeting, Rep. Charles Wilson, second from left, discussed jobs programs with D.C. officials, including Mayor Marion Barry, right. By James K. W. Atherton - The Washington Post