THE FLAP over the FBI's role in secretly channeling information about Chicago Rep. Dan Rostenkowski to an intelligence agent of the Polish government seems to have been a one-day wonder. After seeing the FBI's file on himself, Mr. Rostenkowski said he was satisfied that the bureau did him no harm. There is, he said, little more information in the material the FBI relayed than could be gleaned from standard reference books.

The matter might be left there except for the light it sheds on the need for Congress to pass a strong charter for the FBI setting out the bureau's powers and putting limits on its operations. The widespread immediate reaction to the Rostenkowski story -- that the FBI has been caught in another dirty trick -- underlines the extent to which the bureau's reputation has been damaged. In another era, the matter would have been ignored. It will take years, and a sound set of operating principles, for the FBI to regain the public trust it once enjoyed.

This case involved a routine double-agent operation in which the FBI was feeding information to a person who had reported that he had been approached by a Polish agent. The purpose of such operations is to pinpoint the foreign agent and, eventually, to infiltrate his organization. One danger is, of course, that the information the foreign agent may be seeking can be used for blackmail or other sinister ends.

It is that aspect of the Rostenkowski affair on which the House and Senate intelligence committees should focus. Severe damage to individual liberties can result from handing over derogatory information unless the consent and cooperation of the individual is obtained. Double care should be the rule.

While Rep. Rostenkowski says there was nothing derogatory in what the Fbi provided about him, the committees should make sure that is also the situation in other double-agent cases. If it is, the committees can lay to rest this particular complaint about the FBI's activities in the past. The proposed charter is the proper place for safeguards against potential abuses in the future.