Changes in the Voting Rights Act adopted by the House and supported by nearly two-thirds of the Senate could lead to racial quotas for elected officials and widespread challenges to at-large municipal governments throughout the country, the head of the Justice Department's Civil Rights Division warned yesterday.

As a Senate Judiciary subcommittee finished more than a month of hearings on voting rights, William Bradford Reynolds said that major cities--including Boston, Cincinnati, Baltimore, Memphis, Kansas City and Wilmington, Del.--would all be vulnerable to lawsuits if the proposed changes become law.

Claiming that no group "has a right to be represented on elected government bodies," Reynolds said the administration is willing to support a 10-year extension of the act, but not the one that the majority of Congress is supporting. The version most members of Congress support would extend the 1965 act indefinitely and provide an easier standard for proving violations.

Reynolds said the legislation approved in the House last year on a 389-to-24 vote "would likely lead to the widespread restructuring by federal courts of electoral procedures and systems at all levels of government--from the United States House of Representatives to local school boards--on no more than a finding that the election system is not designed to avoid disproportionate election results."

The administration's major objection is to a provision that local election systems could be considered illegal if they are discriminatory in their effects. Reynolds said the administration wants an "intent" standard requiring proof that local officials consciously intended to discriminate.

Civil rights lawyers have testified repeatedly over the last month that intent is difficult, if not impossible, to prove, especially in older cases where the officials who made the decisions may have been dead for years.

Sen. Patrick J. Leahy (D-Vt.) accused the administration of backing an "emasculated version" of the bill.

Rep. Harold Washington (D-Ill.), speaking for the Congressional Black Caucus, said, "It is patently obvious to the average, fair-minded American . . . that there is something inherently unfair about requiring citizens to prove the subjective intent of political officials."

There are two parts of the Voting Rights Act: an overall provision that applies to the country and a second provision that requires jurisdictions with a history of racial discrimination to get preliminary clearance from the Justice Department for any changes in their voting laws.

The second part, due to expire in August, already has language providing that a violation occurs when a change in election laws would have the effect of discriminating. The dispute is over the first part and up until now, it has not specified whether the standard was to be intent or effects.

The subcommittee on the Constitution, headed by Sen. Orrin G. Hatch (R-Utah), is expected to report out a bill favorable to the administration. But a major fight is expected when the legislation reaches the Judiciary Committee, either later this month or in April.