The Democratic Party plans to unveil its first television commercial of the year today, criticizing Republicans in Congress for not passing bills on HMOs, prescription drugs for Medicare and other subjects while passing a big tax cut.

Democratic officials, who spoke on condition of anonymity, said yesterday that the commercial will air initially in 17 areas. It will be paid for by the Democratic National Committee and the party's campaign organizations in the House and Senate.

Democrats declined to say how much money would be put into the advertising effort; initial indications were that the investment would be relatively modest. The commercial is expected to run at first only in smaller and medium-sized cities, where television time is less expensive than in areas such as New York or Los Angeles.

The commercial is timed to coincide with the end of the year's congressional session, and was previewed for rank-and-file senators during the day.

Party officials said the ad criticizes Republicans for failing to pass bills to extend the solvency of Medicare or Social Security. In addition, it says the GOP did not approve the so-called patients' bill of rights legislation designed to strengthen the hand of individuals in dealing with their HMOs, or a bill to extend prescription drug coverage to Medicare recipients.

The Republican tax cut, totaling $792 billion over five years, was vetoed by President Clinton.

House Republicans have been running commercials for several weeks accusing Democrats of planning to raid the Social Security trust fund to pay for government programs. The commercial has aired in fewer than a dozen congressional districts, also at an undisclosed cost. Democrats, who keep track of GOP spending, say the total expenditure thus far is about $600,000.