The D.C. City Council yesterday approved a proposal to keep the city's property tax rate unchanged through next June, a move that means the average District homeowner will pay about $100 more in taxes because of increased assessments.

In a session that lasted just 10 minutes, ending before some members could get to the chambers, the council approved the tax measure by voice vote and without debate.

The action came one day after the council's finance and revenue committee turned aside requests for election-year tax relief from some homeowners and representatives of commercial interests. Mayor Marion Barry had supported leaving the tax rates unchanged.

The council action keeps in effect a tax rate on single-family homes of $1.22 per $100 of assessed value.

Assessments have risen about 60 percent since that tax rate was established for the 1979-1980 tax year. In that year, the average single-family home was assessed at $57,040; currently, the average home is assessed at $91,095.

The average homeowner's tax bill will be about $1,001, compared to about $900 last year.

The city also is retaining the current rates for rental and commercial property. Rental property is taxed at $1.54 per $100 of assessed value, while commercial property is taxed at the rate of $2.13 per $100 of assessed value.

Council member John A. Wilson (D-Ward 2), chairman of the finance and revenue committee, did not attend the session and could not be reached for comment on his absence. Council member Betty Ann Kane (D-At Large), who earlier had proposed lowering tax rates for senior citizens, stepped off a District Building elevator just minutes after the session was over.

Council member Charlene Drew Jarvis (D-Ward 4), also absent, said she missed the session because a meeting initiated by the city administrator ran too long.

Yesterday's special tax session was the last scheduled meeting of the council before its August recess. The next scheduled council session is Sept. 21, a week after the Sept. 14 primary elections in which party nominees will be chosen for six council seats and the chairman's post.