President Carter's welfare bill moved a step forward in the House yesterday as a special subcommittee approved a new public service jobs program for heads of welfare families unable to find work in the private sector.

The jobs program was steered through by Rep. Augustus F. Hawkins (D.Calif.) only two days after speculation, which was denied by President Carter, that the White House had given up hope of passing the welfare measure in this Congress.

The jobs plan completes basic structural work by the subcommittee on the welfare plan, but many details must still be worked out.

The program will provided about 11 million jobs annually for the beads of welfare families, at salaries ranging from an average of about $7,000 a year in low-wage states in 1982, the first full year of implementation, to about $9,200 in higher-wage states. The average salary nationally will be about $7,700 overall.

A key change proposed by Hawkins permitted average wages for the special jobs to higher in the high-wage states or cities like New York, and lower elsewhere.

Labor unions and municipal spokesmen said the jobs program couldn't work properly if welfare clients taking the special jobs were limited to $7,700 while working alongside a non-welfare employe doing the same work at a subtantially hingher wage. Hawkins said the program will be made part of a community employment and training program for non-Welfare clients and thus won't consist of meaningless make-work positions.

The subcommittee, headed by Rep. James Corman (D.Calif.), left unsettled one key labor issue: the maximum that can be paid anyone under the jobs program.

The administration wanted a flat maximum of $9,600 (primarily for supervisory jobs under the program), but organized labor wanted a higher figure equivalent to that paid for similar jobs in the higher-wage states.

Hawkins said about $10,500 ought to be high enough but he sidestepped the issue by merely putting in the $9,600 figure with the provise that it could be adjusted upward, with the details to be worked out later.

The jobs program will cost about $10 billion or $11 billion a year starting in 1982.

Labor spokesmen were'nt entirely happy with the final jobs provision and said they would fight for the higher maximum for supervisory and other workers..