An increase in payments to city-subsidized day care centers for the children of low-income working mothers has been approved by the D.C. City Council.

Under the legislation, scheduled to go into effect Oct. 1 if allowed to stand by Congress, centers that are now paid $8 a day for each child will receive up to $12.50. An extra payment of $1 for pupil transportation will be continued.

Rates for day care provided in homes also will rise, from $4.50 to $7.

The legislation, sponsored by Polly Shackleton (D-Ward 3), chairman of the council's Human Resources Committee, will make several changes in the day care program designed to ease financial burdens on many of the 27 affected centers.

In its report to the council on the bill, the committee said the centers will be paid on the basis of the number of reservations for children approved by the Department of Human Resources, rather than on the number of children who actually attend.

"A center (under the current arrangements) may be told that it will have 20 DHR-eligible children, reserve these spaces, hire teachers and then never see more than five children," the report said.

Faced with a loss of income, the report asked, "What does a center director do? In the words of one director, 'Stretch the Lincoln right off the penny.' They cut corners: on meals, on equipment, on staff salaries . . . on supplies like books and crayons."

The bill provides for what Lee Partridge, staff director of the council committee, called a modest increase in fees paid for child care by parents whose annual income exceeds $16,190. Only in a rare instances will the increase be as much as $5 a week, she said.

If the bill is signed by the mayor, as expected, it must be sent to Congress for review. Congress has the right to veto the measure, but it has not overturned a council-passed bill since the start of home rule in 1975.