Federal prosecutors said yesterday an allegation by Rep. Charles C. Diggs (D-Mich.) that it is "relatively common" for members of Congress to pay employes for noncongressional work is not enough to warrant a court hearing on why he was indicted.

Diggs claimed in pretrial motions last week that he should not be prosecuted on such charges because other members of Congress have escaped criminal prosecution in such instances.

Assistant U.S. Attorneys Eric B. Marcy and Justice Department attorney John T. Kotelly said such unsubstantiated allegations do not reach legal standards necessary to warrant serious consideration by a judge.

Instead, prosecutors said, Diggs must point out why he is being "intentionally singled out for prosecution" and show that the prosecution is based on impermissible considerations by the persons investigation the case.

The prosecutors said the "artfully written" motion by Diggs' attorneys requesting a hearing in the case gives no indication of why the defense feels Diggs is being singled out for prosecution.

Marcy filed an affidavit saying the "sole basis for the charges . . . was the evidence developed during the investigation," and not the "defendant's political beliefs or legislative activities."

Diggs is charged with diverting $101,000 in congressional payroll funds to his personal use by placing his private firm's employes on the government payroll or by giving his congressional employes raises they had to kick back to him to cover his personal bills.