Two overlapping District of Columbia programs designed to help low-income tenants pay their rent should be coordinated and perhaps merged, the D.C. auditor has told the City Council.

The programs are a "circuit breaker," which grants tax credits to qualified tenants, and a direct rent-subsidy program that was authorized -- but not funded -- when the Council recently voted to extend rent control for three years.

In a report released yesterday, D.C. Auditor Matthew S. Watson, who serves as a sort of civic watchdog, said the two programs are so similar in their purpose that they are bound to create administrative snarls and public confusion. Watson urged the Council and Mayor Walter E. Washington to look closely at the situation before moving ahead.

Watson's report arrived as the Council was preparing to act on a proposed $6.4-million addition to the city's proposed 1979 budget to provide funds for the new subsidy program. If approved, the money would become available Oct. 1.

Council Chairman Sterling Tucker, sponsor of the funding plan, postponed action yesterday and said he would meet with Watson. In a memorandum. Tucker disputed several points made by the auditor and said he would not delay the Oct. 1 start of the subsidy program.

Watson's report was released by Council member Marion Barry (D-at large), chairman of the Council's finance and revenue committee, who said he agreed with Watson's call for caution.

Barry will preside today at a hearing on a proposed expansion of the circuit-breaker program, which affects homeowners as well as low-income tenants. Barry and Tucker are all-but-announced candidates for the Democratic primary for mayor this year. Mayor Washington has not said whether he will seek another term.

Watson, in his report, said the circuit-breaker program was used last year by about 2,000 tenants to obtain rebates for a portion of their rents that otherwise would go to pay real estate taxes.

As such, Watson said, the results of this program show up on the ccity's books as a reduction of tax revenues, while the rent-subsidy program would show up as an expense that must be included in the city's annual budgets.

While aimed largely at the same group of people, Watson said, "the benefits of both programs are not identical; small changes in income, or in rent paid, may make a great difference in choice of program."

"Indeed, a family may apply for a rent subsidy," Watson continued, "only to find that they may have been eligible for greater benefits under the circuit breaker if they had waited. The reverse also may occur. . ."

Tucker, who estimated that the rent-subsidy program would affect 20, 000 tenants in its first year, said the circuit-breaker program applies to some groups of tenants who are above the low-income brackets.

At yesterday's meeting, the Council's first of 1978, Richard Streeter and Jerome Shuman were confirmed for two-year terms as new members of the Rental Accommodations Commission, which helps administer the rent-control law. Five incumbents also were confirmed. Two vacancies remain to be filled.

The Council also enacted and sent to the mayor yesterday a bill to lower the city tax on liquor from $2 to $1.50 a gallon, or by 10 cents a fifth. The measure was initiated by Barry as a way of making D. C. liquor stores more competitive in price with suburban outlets.

The Council also voted final passage on legislation to make a site on the northwest corner of Pennsylvania Avenue and John Marshall Place NW available for a new Canadian Chancery building, housing embassy offices.

The location, five blocks west of the Capitol grounds, is now occupied by two obsolescent city-owned buildings, which will be torn down. The measure transfers the site to the government sponsored Pennsylvania Avenue Development Corp., which will set the price through an appraisal process and sell the land to the Canadian government. The city will get the proceeds.

Both newly enacted bills, if signed by the mayor, require a review by Congress before going into effect, a process that would take until late spring.