Donald J. Trump and his associates have agreed to pay $250,000 in fines and to issue a public apology because they failed to disclose to the state lobbying commission that he had secretly financed newspaper advertisements opposing casino gambling in the Catskills.

The settlement is expected to be ratified at the Nov. 13 meeting of the New York Temporary State Commission on Lobbying, unless investigators unearth new information about Mr. Trump's lobbying activities in New York. It would be the largest civil penalty ever imposed by the commission.

Although there would be no admission of wrongdoing on Mr. Trump's part, he has agreed to spend $50,000 on advertising acknowledging that he had paid for seven ads that appeared last spring under the name of the Institute for Law and Society, an anti-gambling group in Rome, N.Y.

According to several people who have seen the terms of the tentative settlement, Trump Hotels and Casino Resorts would pay $50,000; Mr. Trump's lobbyist, Roger Stone, would pay $100,000; and the institute would pay $100,000.

The settlement was reported yesterday by The Times Union of Albany.

''It's been settled,'' Mr. Trump said. ''We're happy it all worked out nicely.''

Mr. Trump has long feared that competition in the Catskills would undermine the gambling industry in Atlantic City, where he owns three casinos. In the first six months of this year, Mr. Trump reported spending $303,856 to lobby state legislators against gambling and a proposed Indian casino in Monticello, 90 miles northwest of New York City.

But the commission contended that Mr. Trump also should have indicated in his lobbying reports that he had spent another $150,000 on the newspaper ads. Mr. Trump gave the money to Mr. Stone, who created and placed the ads, which criticized Gov. George E. Pataki and highlighted the criminal history of some members of the St. Regis Mohawk tribe.

Mr. Trump vowed yesterday to continue to campaign against gambling in the Catskills and other areas of New York. ''It will destroy the progress that's been made in New York City,'' he said. ''It will drain money out of the city. Instead of buying cars and apartments, they'll be spending money at the casinos.''

Mr. Trump said he also continues to provide financial support for a lawsuit challenging Governor Pataki's authority to approve Indian casinos without a vote by the State Legislature. In August, the Appellate Division of the State Supreme Court reinstated the suit.

Indian tribes own two casinos in New York. Last April, the United States Interior Department approved a plan by the Mohawks and Catskill Development to build a third casino in Monticello. But that project came to a standstill after the Mohawks abruptly abandoned their longtime partner and signed a new deal with Park Place Entertainment, the largest casino company in the world.

Mr. Trump's dispute with the lobbying commission centered not on his opposition to the casinos, but on his failure to disclose all his lobbying activities. Mr. Trump's lawyers contended that the ads constituted free speech rather than lobbying, and did not require disclosure.

Yesterday, Mr. Trump's lawyers said it was cheaper to settle than to litigate, although they still disagreed with the commission.

''We have agreed to make full disclosure and amend our filings in accordance with the commission's view of what constitutes lobbying,'' said Judd Burstein, a lawyer for Mr. Stone. ''We don't agree, but we're acquiescing.''