Senate opponents of President Carter's voter-registration plan yesterday urged that Attorney General Griffin B. Bell be called for questioning after the disclosure of a second Justice Department warning that the plan would increase election fraud.

The plan would permit persons to register on election day at a polling place and then vote in presidential and congressional elections.

The Justice Department's warning came in the form of a telegram sent to all U.S. attorneys by Thomas H. Henderson Jr., chief of the Public Integrity Section of the department's Criminal Division.

"We recognize that election-day registration may increase the opportunity for election fraud," the telegram said.

Sen. Strom Thurmond (R-S.C.) gave the Senate Rules Committee a copy of Henderson's telegram after assailing Carter's plan as "opening the door to more election fraud than anything I have ever heard of."

On Thursday, the committee obtained a copy of a memo by Craig Donsanto, a career lawyer who heads the Election Unit of the Justice Department's Criminal Division, warning that the bill has a "tremendous potential for fraud."

Sen. James B. Allen (D-Ala.), a committee member who has joined Republicans in attacking the bill, suggested that Bell be called to "shed further light on the position of the Justice Department" in light of these developments.

Allen said Bell had "shot from the hop" when the Attorney General testified before the House Administration Committee on April 6 in support of the bill. Allen said Bell apparently had never read the measure at the time of his testimony.

Sen. Howard W. Cannon (D-Nev.), the committee chairman, said Bell had been invited to testify at the start of its hearings but that Bell instead sent Deputy Attorney General Peter F. Flaherty to testify for the department.

Cannon said he didn't think the committee should interfere if the Attorney General wanted to have his deputy testify. However, Cannon said he would ask the Justice Department if it wants to supplement its testimony and also find out if Bell wanted to appear or have Flaherty testify again.

Flaherty, when he was before the committee Wednesday, testified that he had not read Donsanto's memo. He subsequently supplied the committee with a copy of the memo after initially declining to do so and asserting a claim of executive privilege.

The memo reached Congress Thursday, shortly after the House committee and approved the instant registration bill by a 17-to-8 party line vote following the adoption of tighterning amendments intended to increase safeguards against fraud.

Henderson's telegram to U.S. attorneys said that Flaherty was to testify before the Senate committee on May 4 and planned to suggest that the legislation "serve as a vehicle for requiring all of the states to have voters sign poll lists or rosters upon entering the voting booth, a ballot security procedure which we believe many states do not presently have."

"Such poll lists or rosters have been particularly useful tools in the discovery and the prosecution of exection fraud," Henderson told the prosecuting attorneys in requesting they supply information on whether voters in their states are required to sign any kind of list before or after voting.

Cannon agreed at the urging of Thurmond and Griffin to ask the Justice Department to supply the committee with the attorney's responses.