Responding to strong opposition from all segments of Washington's legal community, the D.C. Bar's Ethics Committee has substantially watered down its proposal to block the "revolving door" that allows lawyers to move freely between government service and private practice.

The new proposal, which goes before the Bar's Board of Governors Tuesday, contains a "grandfather clause" that would exempt lawyers presently working for the government, but would apply to lawyers who join the government after final approval of the policy.

Moreover, the porposal would make it easier than one drafted a year ago for law firms to win exemptions from some of its conflict-of-interest restrictions, and would allow government lawyers to take jobs with law firms - but not private companies - that they had substantial dealings with in their last year of government service.

The committee's proposal still represents the first attempt by an organized bar to deal specificially with the question of the "revolving door" situation. The situation has drawn increasing criticism from consumer groups and President Carter, among others, for giving an unfair edge to big business in its dealings with the federal bureaucracy.

The proposal, which must be approved both by the Bar's Board of Governors and the D.C. Court of Appeals before it can take effect, goes beyond the regulations of any other bar association and federal conflict-of-interest laws.

It all started four years ago when two lawyers who left the government for private practice asked the ethics committee whether it would be right for them to represent a company tryingr to renegotiate a contract that they had something to do with while they were working for the government.

William H. Allen, chairman of the Ethics Committee, called that inquiry "a blessed opportunity to fashion rules tailored to the particular problems that are posed" by practicing law in Washington.

While other Washington lawyers complained in comments filed with the ethics committee that the new rules would put lawyers here at a competitive disadvantage with lawyers in cities with less stringent regulations, Allen said that "there is every reason for the D.C. Bar to have its own set of rules . . ."

"Other bars may very well follow out lead," he continued in a memo to the D.C. Bar's Board of Governors, "but their possible choice not to do so is not a reason for us to withhold action."

As revised by the ethics committee as a result of 89 comments on last year's proposal, most of them opposed to substantial parts of it, the new rules would:

Disqualify for all time all members of a firm from taking a case in which one member played a major role while working for the government. Likewise, all members of a firm would be barred for one year from representing a client that one member of the firm had substantial contact with in his last year of government service. But a law firm could get a waiver from the restriction, if the government agreed, by swearing that the lawyer involved will have nothing to do with the case and will get no income from it.

This disqualification includes attorney's who drafted or approved government regulations, but was pared down to exclude lawyers who merely interpreted the regulations.

Ban for one year a government attorney's taking a job with a company - but not a law firm - that he had major dealings with in his last year of government service.

Originally, the committee would have banned government lawyers from taking jobs with anyone - law firm, company or individual - with whom they had major dealings in their last year with the government.

"We made an accommodation to heart-rending pleas that it would make it impossible for many government attorneys to find a job," said Allen.

Restrict lawyers who join the government from taking part in cases for one year that they or other members of their law firm dealt with while in private practice. The committee made an exception for lawyers appointed by the president and requiring confirmation by the Senate, which presumably would consider any conflict of interest, and lower-ranking lawyers who were given an OK by a presidential appointee.

The regulation also would disqualify judicial law clerks - but not counsels to congressional committees or aides to congressional committees or aides to congressmen or senators - from taking part in cases they dealt with while on the government payroll.