The government promotion ladder has become partially blocked because of the current 25 per cent hiring cutback in federal agencies. Hiring and promotions may not return to normal levels before mid-June.

President Carter ordered the hiring reduction in March in order to force agencies to slim down for new personel ceilings by filling only three of every four vacancies. The new job ceilings will be assigned by the Office of Management and Budget on behalf of the President.

At the time Carter imposed the 3-for-4 rule, it was targeted to end by mid-April at the latest, but it still is causing withdrawal pains in some agencies and has blocked promitions.

White House aides had hoped to see substantial federal job reductions in March, the first full month under the 25 per cent hiring cutback. But, as this column reported last Monday the actual decline in permanent full-time employment amounted to only 1,224 jobs in a work force of 2.4 million full timers. The main reason for the relatively small reduction is that, despite the 3-for-4 rule, agencies were allowed to hire persons who already had been promised jobs.

otal federal employment for March jumped by about 5,000 jobs, but the increase was in part-time and temporary employees.

Officials expect an even greater drop in permanent full-time federal employment when data for April and May are eavailable.At the same time, they predict that promotions will be even less available during the partial hiring freeze.

The hiring freeze has caused unease among many government workers about their jobs, and many who had planned to retire or seek work elsewhere have stayed put, slowing the normal attrition rate.

The vast majority of jobs becoming available are in middle and lower grades, especially in the clerical ranks. Because the jobs are at relatively low level, most persons put into them are hired from the outside or via lateral transfer rather than promotion.

Higher grade workers are staying put during the freeze period, so jobs that normally would open up and provide promotion potential are not being vacated.

National Federation of Federal Employees has more than 100 top officials here from the field this week for a lobbying session with the Senate and House. Union members will staffers of the Senate Governmental Affairs Committee and breakfast again Wednesday with the House Post Office-Civil Service Committee.

NFFE is trying to persuade Congress to curb contracting of federal work and enact a labor-management law covering Uncle Sam's 2.8 million employees.