Washington ? Atty. Gen. John Ashcroft’s plan for next-day destruction of gun background check records could impair law enforcement’s ability to keep firearms out of the hands of prohibited purchasers, congressional investigators said.

The General Accounting Office said destruction of the records after one business day would prevent law enforcement from identifying gun buyers who were wrongly approved initially but later determined ineligible. Gun control groups used the GAO’s preliminary findings, contained in a letter to Sen. Richard Durbin, D-Ill., to bolster their opposition to the Ashcroft plan.

The attorney general announced last June that he would shorten the FBI’s current 90-day retention period to one day, a policy shift that had been advocated by the National Rifle Assn. The proposal is not yet in effect.

FBI officials told the GAO that more than 100 firearm-retrieval actions were initiated during a four-month period last year on the basis of National Instant Criminal Background Check System records kept for more than a day.

In a letter made public Thursday, Durbin asked the attorney general to withdraw the proposal, saying it would “have a serious negative effect on our shared goal of keeping guns out of the hands of felons, foreign terrorists and others who wish to obtain firearms illegally.”

Justice Department officials offered no immediate comment.