RENTON, Sept. 19 — Gov. Christine Todd Whitman weighed in on the United States Senate race in New Jersey today, urging Jon S. Corzine, the Democratic candidate, to remove any lingering "shadow of doubt" about his finances and release his personal income tax returns.

The Republican governor, who is supporting Representative Bob Franks, the Republican in the race, praised Mr. Corzine for disclosing his charitable donations on Monday but chided him for not following her own example and making his tax returns public.

"Mr. Corzine, half disclosure is no disclosure at all," the governor began in a letter to Mr. Corzine that was given to reporters tonight by the Republican State Committee. It was her second letter to Mr. Corzine on the subject in the last few weeks.

Mrs. Whitman neglected to mention, however, that she resisted similar demands for months during her first-term election campaign in 1993. She eventually released returns for 1989 through 1992, holding one of them back until less than three weeks before the election, in which she defeated Gov. Jim Florio.

Mr. Corzine has been equally adamant about withholding his tax returns. He has released one-page abstracts of his earnings and taxes paid for 1996 through 1999. But he has refused to go further, saying he is prevented from doing so by a confidentiality agreement with Goldman, Sachs & Company, the investment bank he headed until last year.

Mr. Corzine's spokesman, Tom Shea, brushed off the governor's letter tonight, noting that she had sent a similar one several weeks ago on official state stationery.

"Christie Whitman and Bob Franks have been politicians so long that they don't understand straight talk when they hear it," Mr. Shea said. "Jon has said he has a contract. He intends to honor that contract, and he intends to keep his word to the voters of New Jersey when he gives it."

The back and forth came a day after Mr. Corzine, who has been repeatedly accused by Mr. Franks and others of trying to buy a Senate seat, disclosed records of his charitable giving for 1999 and 2000. Included among $10 million in gifts were more than $100,000 in donations to four groups whose leaders or sponsors later endorsed Mr. Corzine.

In December, for example, he gave $25,000 to St. Matthews A.M.E. Church in Orange, N.J., whose pastor, the Rev. Reginald T. Jackson, is the head of the Black Ministers Council of New Jersey. But in April, when Mr. Jackson and 19 other pastors endorsed him, Mr. Corzine stood by silently as another minister denied that any of them had received donations from Mr. Corzine.

Today, State Senator Louis F. Kosco, a Republican from Paramus who is chairman of the law and public safety committee, called on the Internal Revenue Service to investigate the tax returns of Mr. Corzine's charitable foundation, through which he made most of his donations. Mr. Corzine indicated in the return that he did not give more than $100 "for political purposes." Mr. Kosco said he believed Mr. Corzine had violated federal tax law but based his allegation solely on news accounts.

Mr. Shea responded tonight by demanding to know "the specific contributions they claim are political." He added, "If the Bob Franks campaign is trying to imply that the votes of African-Americans in New Jersey can be bought, then he should have the courage to step out from behind his surrogates and make the accusation himself."

A spokesman for Mr. Franks, Peter DeMarco, responded: "Why is no one coming to Jon Corzine's defense? The silence is deafening."

In fact, Mr. Corzine came under attack from a fellow Democrat today, albeit one with little party loyalty, in the form of Bruce Afran, a civil rights lawyer, who announced his own candidacy for the Senate under the Green Party heading. He remains a registered Democrat, he said, because voters are unable to register as members of third parties under New Jersey law.

"We've seen the corruption of the entire Democratic Party through the influence of Jon Corzine," Mr. Afran said, referring to Mr. Corzine's previously disclosed contributions to Democratic groups and candidates, and to the $35 million he spent winning the party's primary in June. "Now the Corzine campaign is effectively corrupting churches."

He even suggested that Representative Franks, the Republican, could be the lesser of two major-party evils. "I think it would be far healthier to elect an honest conservative, who has a long history behind his opinions, than to elect a man who is using his fortune to create a false image of himself as a liberal," Mr. Afran said.

Mr. Shea dismissed Mr. Afran's assertions as efforts by an obscure third-party candidate to attract attention.