Two Washington attorneys were suspended yesterday from practicing law in federal court here for at least one year because of a four-line decogatory comment concerning a federal judge that appeared in court papers signed by the attorneys more than six years ago.

The suspension was filed against attorneys Donald J. Chaikin, whose offices ate at 1225 Connecticut Ave. NW, and Leroy Nesbitt, whose offices are at 1140 Connecticut Ave. NW.

They are believed to be the harshest suspensions meted out here in recent years in any disciplinary action in which no criminal charges have been filed or are anticipated against the lawyers involved.

Both attorneys have testified under oath within the past two months that the comment about the judge was untrue, and contend that they have no explanation of how it got into the appellate brief they filed. They testified, however, that one of the defendants whom they were representing was a disbarred lawyer who had access to the brief before it was filed.

The suspension order issued yesterday was signed by U.S. District Judges Barrington Parker, Thomas A. Flannery and Charles R. Richey, who conducted a brief trial on the charges against the two attorneys after the case was referred by the court's committee on grievances.

At the trial, attorneys for both men again said - and the accused attorneys themselves testified - that the comment about the judge was untrue. They argued against any punishment, however.

The three judges found that Chaikin and Nesbitt "were careless and negligent and demonstrated an indifference to the importance of maintaining the integrity of the legal profession," and that their conduct was "unprofessional, improper and prejuducial to the administration of justice."

The suspensions grew out of a statement that appeared in the appellate brief filed by Chaikin and Nesbitt in a 1971 criminal case.

The 41-page brief included the following comment: "The trial judge sought to dissuade co-counsel from representing the appellants with the statements that no future political backing would be accorded counsel and that he would not be paid by the defendants (see minutes)."

There was no further discussion of that point in the brief, and the reference to "see minutes" did not appear elsewhere. The convictions of the three defendants on fraud charges was affirmed by the Court of Appeals.

The statement apparently went unnoticed until the defendants filed a request for a new trial on constitutional grounds in 1974, and won a new hearing that occurred last summer in federal court.

During that hearing last summer, Chaikin and Nesbitt were called to the witness stand and questioned about the statement. When they said the comment was untrue and that they could not explain it further, U.S. District Judge George L. Hart Jr. referred it to the grievance committee.

Nesbitt is a prominent defense attorney who has been a member of the bar here for 16 years and has been mentioned in the past as a possible candidate for a judgeship. He has represented defendants in many major criminal cases, including a man who was convicted of murdering two FBI agents here several years ago.

Chaikin's attorney, Albert Ahern, said last night that he would appeal the suspension because he feels it is excessive punishment for what the judicial panel described as "negligence."

The suspension takes effect May 16. It does not affect Chaikin's and Nesbitt's privilege to practice in the local court system, although suspension orders are routinely referred to that court's disciplinary system.