With less than two weeks remaining for seniors to sign up for the new Medicare prescription drug benefit, an independent review has found that Medicare's telephone operators frequently give callers false or incomplete information, reviving calls by Democrats to extend the May 15 deadline.

The report released yesterday also found that Medicare's written promotional materials used too much technical jargon, that call waiting times lasted from a few minutes to almost an hour, and the government Web site was so confusing that some people gave up before completing the process.

Posing as seniors or individuals helping a senior, investigators for the Government Accountability Office placed 500 calls to 1-800-MEDICARE and found that about one-third resulted in faulty information or none at all.

The quality of service varied widely. On a question relating to which seniors qualified for discounted plans, customer service representatives gave correct information 90 percent of the time.

When asked which drug plans were most appropriate and least expensive for an individual, however, the accuracy rate fell to 41 percent. Often, Medicare representatives incorrectly told callers they required personal data such as a Social Security number. In fact, they can provide general information but would be able to give more sophisticated guidance with the personal data.

Although Bush administration officials have acknowledged early glitches, they said the GAO study did not take into account recent improvements and failed to recognize that seniors can use multiple sources of information to get the most complete picture.

"The report is unfortunate, incomplete, out of date and inaccurate," said Medicare spokesman Peter Ashkenaz. He said it was unfair to criticize operators for requesting personal data that would lead to more detailed assistance.

The new drug coverage for Medicare's 42 million senior and disabled beneficiaries went into effect Jan. 1. Although the program is voluntary, retirees who sign up after the May 15 deadline will pay higher premiums. So far, about 30 million people are enrolled in a Medicare prescription plan or one offered through an employer's retirement plan.

Although the findings did not surprise advocacy groups that have complained that the program is unnecessarily complicated, the report added fuel to the ongoing political brawl over one of President Bush's signature domestic achievements. Democrats, who largely opposed the legislation, say the program amounts to a windfall for insurers and prescription drugmakers and a fresh headache for many retirees.

"Because of inaccurate or incomprehensible information, seniors haven't been given a fair shake," said Michigan Rep. John D. Dingell, the ranking Democrat on the House Energy and Commerce Committee. "Seniors can't make good choices if they can't get good information. And these problems confirm that this privatized prescription drug plan is inherently too complicated."

Medicare chief Mark B. McClellan defended the program in an appearance before the House Ways and Means Committee yesterday.

Although the 7,500 customer service representatives did not know which callers were from the GAO, the administration was alerted to the investigation, said Leslie Aronovitz, director of the division responsible for the report. In addition, when Medicare operators initially gave an inaccurate answer, GAO investigators "bent over backwards to try to give them as much leeway as we could," she said.