WASHINGTON (AP) _ The General Accounting Office has agreed to pay $3.5 million to more than 300 current and former black workers who accused Congress' investigative arm of racial discrimination, lawyers in the case and the GAO announced Tuesday.

The GAO also agreed to promote 32 of the blacks as part of the settlement, which ended two class action complaints filed with the GAO and the Equal Employment Opportunities Commission.

Kerry Alan Scanlon, of the Washington Lawyers' Committee for Civil Rights Under Law, said civil rights lawyers believe this was the largest amount of money awarded to black professionals in a job discrimination case - in or out of government.

The settlement affects blacks who were denied equal opportunities for promotion to upper-level positions from 1976 to present. The exact number in the class will not be known until applications for the monetary awards are received.

The agreement is expected to take effect in September, following a month- long comment period, Scanlon said.

Payments for individual class members are expected to range from several thousand dollars to about $20,000, depending on how long the individuals were eligible for promotion - and whether they're still employed by GAO. A majority of the class members work at GAO headquarters in Washington or in one of the agency's 15 regional offices.

Most of the class members are GS-12s or GS-13s, government pay grades with current salaries of $31,600 and $37,600 respectively. Most of them were responsible for writing and evaluating GAO's reports to Congress.

''I conclude and recommend that GAO find that GAO discriminated intentionally and unlawfully against black evaluators because of their race....'' said EEOC complaints examiner Chester F. Relyea in his findings.

''There was substantial evidence of racist attitudes among GAO's managers ... and although this problem did not seem to be greater at GAO than in many other organizatios, it was sufficiently prevalent to make it a matter of concern in any kind of evaluation system.''

Under the GAO's promotion system, a panel reviewed applications for upgrading and selected a list of those best qualified. A selecting official then would chose someone from the list.

According to Scanlon, supervisors making recommendations to the panels used code words for blacks that gave them a lesser chance of gaining promotion.

Scanlon said that while the number of black evaluators has been increasing, they received only 90 competitive promotions out of a total of 1,600 during the past eight years. A total of 3.9 percent of blacks applying for promotion were successful, compared to 5.2 percent of the whites in the affected categories.