Federal workers who must choose a health insurance plan by Dec. 23 are having unprecedented difficulties getting the information and forms they need to help them evaluate medical coverage options, according to congressional offices and government employe groups who have been deluged with calls from anxious civil servants.

The Office of Personnel Management, after delays in distributing health plan brochures and cost/benefit comparisons, last month extended the "open season" period for shopping around among health plans through Dec. 23. But the material, especially at larger agencies, is still in short supply, and government retirees say they are having the most trouble picking a plan.

"I've asked OPM for information, but I haven't gotten anything back," said Irvin Peak, a retired government worker from Bethesda who is looking for a plan with good dental coverage.

Peak was among about 120 current and retired federal employes who turned up last night at Montgomery College in Rockville for a health symposium designed to help government workers choose the best plan for them.

The symposium, sponsored by the Federal Government Service Task Force chaired by Rep. Michael D. Barnes (D-Md.), was a 75-minute videotape of a program held last week in Silver Spring. So many people had to be turned away then for lack of space that the task force taped the health plan discussion and is holding "instant replays" around the region on a reserved-seat basis.

Live symposiums for larger groups are continuing to be held, sponsored by the task force and other area members of Congress. Additionally, a cable firm in Prince Georges County plans to show another taped health program to federal workers in that area.

"We're trying to decide between Aetna and Blue Cross/Blue Shield," said Lucile Yensen, attending the program with her retired worker husband, Arne. "It's hard to compare on the brochures."

In a statement passed out to the group, Barnes blamed OPM for what he called the "unconscionable absence" of health insurance information. He said this contributed to the heavy turnout at earlier symposiums. His complaint was similar to one earlier this week from other congressional and government employe spokesmen.

"People need to know what their options are and the differences in the benefits provided for the monies expended," said Martin Wish, a spokesman for Maryland chapters of the National Association of Retired Federal Employes (NARFE). Nearly 23 percent of federal retirees and almost 75 percent of their survivors receive less than $500 a month in annuities, he said.

The problem is particularly acute now because, though the government pays roughly half the overall costs, premiums for enrollees shot up 30 percent this year and will jump another 24 percent in January. Many retirees, especially those enrolled in the comprehensive but increasingly costly high-option Blue Cross/Blue Shield plan, are shopping for less costly coverage.

Depending on the health plan, 400,000 federal workers and retirees here, plus their families, and 9.2 million people covered nationwide, could end up paying premiums next year ranging from $380 to $1,600. Such price variations have encouraged comparison shopping.

"There's never been this kind of dilemma before," said Tom Deyulia, staff director of the House Compensation and Employee Benefits sub-committee. He said that before last year, when OPM reduced benefits while increasing premium costs, the Federal Employees Health Benefits Program had been "much more stable," with only 5 percent of its enrollees electing to switch plans.

OPM, while conceding it was "a little late" getting health brochures out, says it has now distributed the material to about 80 percent of the agencies and 95 percent of the retirees and expects plan selections to proceed smoothly.

"This is not a distribution problem but an interest problem," said James Bryson, an official with OPM's office of insurance programs. "There's a much greater interest among employes and annuitants who have resisted changing plans in the past."

Bryson said 20 percent of the employes and 4 percent of the annuitants switched plans last year, with more expected to change plans this month. Active employes are supposed to get materials at their personnel offices. Retirees are mailed an updated brochure about their present plan and a return post card for checking off additional materials they may want, including a form for switching plans.

But some federal employes report they still cannot get their own brochures and must copy them on agency copying machines. Retirees say OPM "is not that fast getting back to us," particularly with "switch" forms.

Health information calls to Maryland Democratic Reps. Barnes and Steny Hoyer and Virginia Republican Reps. Frank Wolf and Stan Parris have been steady to heavy, aides said. A Hoyer aide said people have complained of getting "bounced around" at OPM. A Parris aide said confusion has been substantial, adding that even when employes and retirees get the material, many "still can't figure it out."

Robert Honig, staff director of the task force, said agencies "just weren't prepared to deal with the increased interest in switching plans." Several agencies, he said, have been calling to get the videotape.

Interested federal workers and retirees in the District and in Montgomery, Prince George's, Fairfax and Arlington counties are urged to contact their congressional representative or the task force for information about future presentations.