A top executive at Vernon Savings and Loan Association of Texas -- which required the costliest federal bailout ever of a savings institution -- has agreed to plead guilty to filing a false financial statement for Vernon and to cooperate with a federal investigation of crime in the state's S&L industry, the Justice Department announced yesterday.

The agreement by John G. Smith, a former senior executive vice president of Vernon, to plead guilty is potentially embarrassing for House Speaker Jim Wright (D-Tex.) and other Democrats. Wright has acknowledged intervening to get regulators to go easy on the troubled S&L, which was a big contributor to Democratic candidates in Texas.

In addition to Smith, three other businessmen have agreed to plead guilty in connection with the Texas probe, the Justice Department said. The Justice Department also announced a three-count indictment of a fifth businessman.

The legal actions are the first to come from the task force the federal government formed early last year to probe allegations of massive fraud and abuse at Texas S&Ls. The Justice Department agreed to accept the guilty pleas in exchange for promises by the defendants to help the government prosecute dozens of executives believed to have misappropriated billions of dollars from scores of Texas S&Ls that have failed or are near collapse.

The department said the four agreed to cooperate in exchange for lenient treatment from the government.

Justice Department lawyers in Washington said they believe some of the criminal activity they uncover in Texas eventually will be tied to fraud and abuse at S&Ls in California and in the Northeast.

"This should signal that the {Justice Department} organization means business," said William Hendricks III, chief of the Justice Deparment's Fraud Section. "We're not going to be plodding along for years."

Hendricks said that winning an indictment and several agreements for guilty pleas just eight months after the Texas task force began its probe will create an atmosphere that will prod many executives to come forward.

"There's a reaction that there's no point in prolonging the inevitable, that they {S&L executives} might as well come forward and tell what they know," he said.

U.S. Attorney Marvin Collins of Dallas expressed similar optimism at a press conference in Texas.

"This is a significant step early in the life of the task force," the Associated Press quoted him as saying. "We're now seeing the first results of this investigative effort. We're hopeful this early success tends to cause others who are under investigation to decide what they are going to do."

More than 50 agents and lawyers from the FBI, the Internal Revenue Service, the Justice Department, the U.S. attorney's office and the Federal Home Loan Bank Board are involved in the investigation, which began last summer and is expected to last three to five years.

Officials in Dallas refused to say how many people are under investigation, but confirmed to the Associated Press that they were looking into irregularities at 25 thrifts and 10 banks in Texas.

In addition to the guilty plea of former Vernon executive Smith, the Justice Department announced yesterday that:

A real estate broker, Donald W. Nahrwold, was indicted on three counts of conspiracy, aiding and abetting misapplication of funds and making false statements to federal regulators in connection with an alleged 1983 loan kickback scheme at the State Savings and Loan Association of Lubbock.

The department said it has accepted guilty pleas from two other executives in connection with the scheme. The S&L owner, Tyrell G. Barker, has agreed to enter a guilty plea to a charge of misapplication of funds in the scheme, through which he received a $100,000 kickback on a $2 million loan.

Former real estate broker Larry K. Thompson pleaded guilty on charges of misapplication of funds at State S&L.

Former Commerce Bank of Plano chief executive Sam Thomas III has agreed to plead guilty to misrepresenting the financial condition of his bank.

Vernon, State Savings and Loan Association and Commerce Bank all have failed.

The government closed Vernon in March and then reopened it in November with a $1.3 billion infusion. The most costly rescue of a financial institution was the government's $4.5 billion bailout of Continental Illinois Bank & Trust of Chicago.

Justice Department investigators said that the scope of the 8-month-old task force operation dwarfs the government's separate four-year investigation of the I-30 condominium case in Dallas, which has led to 95 indictments for fraudulent practices in the management of condominium complexes in a Dallas suburb.

Since last summer a federal grand jury has subpoenaed financial records of the state's top S&L regulators, a former governor, former lieutenant governor and 99 others in connection with the task force investigation.

The task force was formed in response to a widening financial crisis among S&Ls across the country, especially in the Southwest. Regulators estimate that fraud is involved in more than 50 percent of all bank and S&L failures.

Justice department lawyers would not comment on whether they expect any indictments of federal or state officials.

The grand jury subpoena list includes Texas Savings and Loan Commissioner L. Linton Bowman III, former Texas Gov. John Connally, former Lieutenant Gov. Ben Barnes and Gene Phillips, the chairman of Southmark Corp.