Harry M. Singleton, the Republican nominee for D.C. delegate, yesterday released his federal and District income tax returns for the last five years, called on Eleanor Holmes Norton to do the same thing and referred to his Democratic rival as the "Leona Helmsley" of Washington.

In escalating his criticism of Norton's failure to file D.C. income tax returns for the past seven years, Singleton compared the Georgetown University law professor to the New York City hotel magnate who was convicted on tax evasion charges.

"Mrs. Helmsley, you'll remember, with all of her millions, didn't think she should have to pay taxes either," Singleton said at a news conference yesterday. "For her, and obviously for Eleanor Holmes Norton, paying taxes is something that only little people do."

With his action, Singleton sought to keep the pressure on Norton, who has declined to release her federal and D.C. tax returns.

Norton has acknowledged not filing District tax returns since 1982, saying that her husband handled the family finances and she was unaware of the failure to file. She recently paid nearly $90,000 to settle her debts with the D.C. government, including penalties and interest from back taxes owed.

Norton has released what she says are summaries of information in her tax returns. But she has declined to release the actual returns, saying that her husband considers such a release an invasion of his privacy.

A Norton campaign source said Edward Norton continues to hold to that position.

Eleanor Norton's campaign manager, Donna Brazile, said yesterday, "The actual information regarding Mrs. Norton's taxes between 1982 and 1989 has been disclosed . . . . We have no further information today to disclose."

Singleton challenged this posture at the news conference yesterday, saying that "only through complete and total disclosure will the voters be able to make an informed choice about who their delegate will be."

Singleton said Norton's actual tax returns need to be released "to see if there's not some other thing that might be lurking there. They failed to file and pay local income taxes for some seven or eight years. How do we know what's remaining to be revealed about the tax situation?"

"She's just been feeding it to us in dribs and drabs," he said. "I've put my taxes out on the table now. I ask her to do the same."

Singleton is a lawyer and lobbyist who held a number of sub-Cabinet positions in the Reagan administration.

According to his returns released yesterday, Singleton reported a total of $313,368 in income for the tax years 1985 through 1989. He paid a total of $13,061 in D.C. taxes and $40,938 in federal taxes, the returns showed.

The returns also show a sharp drop in income between 1985, when Singleton earned $74,273, and 1989, when he earned $38,314.

The returns were all signed by Singleton and dated before the April 15 deadline for each of the years in which they were due.

Jeffrey B. Shields, an accountant who accompanied Singleton to the news conference, said he reviewed the returns and found they were "prepared properly" and that Singleton paid the proper amount to federal and local governments.