For weeks now, the people who represent or speak for federal employes have been feverishly marshaling their forces--trying everything they can think of--to stop the inclusion of new government workers in the proposed $165 billion Social Security rescue bill.

The unions and other federal employe and retiree groups have bought television and radio spots attacking the proposal and bused in thousands of rank-and-file members to lobby Congress, including about 4,500 postal employes who did some arm-twisting of their own on Capitol Hill yesterday.

The region's congressional delegation, which represents more than 345,000 civilian employes, the largest concentration of federal workers in the country, has tried to amend its constituents out of the Social Security package or delay their inclusion by one year.

Despite such intense opposition--fueled by fears that putting new federal hirees under Social Security would bankrupt the civil service retirement fund--very few of the bill's detractors hold out much hope of blocking its passage.

"It looks like this thing is cast in stone at this point, although we've sure been trying," Rep. Michael D. Barnes (D-Md.) said yesterday.

The main problem with stopping or amending the bill, according to members of Congress from the Washington area, is that the Social Security measure is a delicate package of compromises worked out by a presidential advisory commission and endorsed by the House and Senate leadership. Pull one thread, the argument goes, "and the whole sweater will unravel."

But this hasn't stopped Barnes or other Democrats and Republicans with federal worker constituents from trying to do some reknitting.

Rep. Marjorie S. Holt (R-Md.) took the rescue plan to task in a letter to the chairman of the House Ways and Means Committee. Signed by 34 House Republicans and Democrats, including nine from the Washington area, it asked the committee to delete coverage of new federal hires.

Barnes and Rep. Steny H. Hoyer (D-Md.), using information supplied by the Federal Government Service Task Force that Barnes chairs, held their own meetings last week with members of the committee and the House leadership. They urged delaying inclusion of new federal workers pending a study. They warned that the proposal could cost new hires, forced to contribute to two retirement systems, a quarter of their take home pay.

Rep. Stan Parris (R-Va.) lobbied the chairman of the House Rules Committee to allow introduction of such an amendment on the House floor. Rep. Frank R. Wolf (R-Va.) has worked both sides of the aisle trying to delete federal workers from the bill and pushing for creation of a bipartisan commission to study federal worker concerns.

All to no avail.

The House Ways and Means Committee, after defeating efforts to delete federal workers, approved the legislation last night and sent it to the full House. The House leadership has refused to budge on permitting such an amendment on the floor.

Complicating the lobbying for federal employes has been a recent defection of Republicans from the task force headed by Barnes. Parris said "the thing got so blatantly partisan, I just pulled out." Barnes said even Republicans are bound to clash with "a president that's out to do in their constituents." But he concedes he may have some bipartisan fence-mending to do because federal worker representatives "can't afford to be fighting among ourselves."

Meanwhile, Parris has ordered 20,000 "Parris Resistance" buttons as part of his attack on several antifederal-worker issues and vows to "go down with the ship" on the Social Security bill. Others say they are trying to look at the situation more realistically.

"From the moment the leadership endorsed the package, it's been a very uphill battle," Hoyer said.

Some say it has been a nasty and bloody battle as well.

Federal employe unions have fought for years to hold onto a separate and comparatively generous retirement system, often described as the "golden handcuffs" that attract and keep government workers. In addition to Reagan-initiated reductions-in-force and more expensive health insurance, they face new budget proposals to freeze pay, penalize early retirement and eliminate cost of living adjustments due retirees in 1984.

"We don't want the civil service retirement system disrupted to achieve a very short term revenue gain for Social Security," argues Jerry Klepner, a National Treasury Employees Union official who is treasurer of FAIR (Fund for an Independent Retirement). Neither does he buy the argument that the package can't be tampered with: "It's a rationalization--one can find safety in an overall package."

FAIR has spent more than $250,000 on advertising to fight the proposal, and unions have made it their number one priority--even at the risk of alienating some of their usual supporters in Congress.

"We've put together a package that will save the federal-worker pension," said Rep. William D. Ford (D-Mich.), chairman of the House Post Office and Civil Service Committee, who has promised to maintain current federal employe retirement benefits no matter what. But the unions say they don't trust Congress to protect them, particularly after what's happened to federal employes the past two years.

Ford and other normally sympathetic members of Congress want federal employe groups to shift their focus to the Reagan budget, which Ford says could have a far worse impact on government workers. And they warn that putting members in the position of choosing between Social Security constituents and federal-worker constituents "is burning up good will" the employes may want later.

Klepner and others disagree, saying they think Congress has been "sensitized" to federal-worker problems during the Social Security fight. "Enough is enough," Klepner argues.