J. Walter Jones, a Maryland banker once described by federal prosecutors as a "bagman" for cash kickbacks to Spiro T. Agnew, was fined $5,000 and sentenced to three months in prison today for soliciting an illegal corporate contribution to the 1972 Republican presidential campaign.

Jones, who pleaded guilty, would have avoided serving any time had he not followed his plea with a letter to U.S. District Judge R. Dorsey Watkins attempting to downgrade his role in the contribution.

The angry judge interpreted the letter as an effort by Jones to qualify his guilty plea. "I would not have done what I am going to do had it not been for the letter," Watkins said as he sentenced Jones to two years in prison with all but three months suspended.

Former Vice President Agnew, who resigned after pleading no contest to income tax charges stemming from accepting the kickbacks, issued an angry statement also today.

"Mr. Jones has been punished because of his association with me," Agnew said. "Rather than falsify his testimony (in the Agnew case) in exchange for immunity for himself, he chose to tell the truth. As a result of 'not cooperating' with the prosecutors in the case against me, he has been singled out and persecuted for a campaign law offense that has been overlooked in hundreds of instances throughout the U.S.

"He has been prosecuted for the unproved allegations against me, which have nothing to do with the offense for which he has been sentenced."

A contrite Jones explained to the judge that the letter was not an attempt to "be untruthful, but to close my eyes to the situation."

"Mr. Jones," said Watkins, "I am really sorry. I am . . . this time it's very hard.

Alone except for his attorney, Jones cast a much different figure than in the days when his close friend Agnew was Vice President and Jones was an influential figure in Republican Washington.

Originally, Jones was charged with nine counts, including extortion and conspiracy, in connection with his activities as head of the Maryland Finance Committee to reelect the President in 1972. Jones pleaded guilty to one count of soliciting the money as part of his plea bargain.

Federal prosecutors claim Jones solicited $10,000 from the Singer Co., a major government contractor for helicopter, ship and aircraft parts.

Jones, according to a statement of facts prepared by the U.S. attorney arranged to "launder" the contribution through a bogus $15,000 consulting fee to engineer Lester Matz, who would keep $5,000 to pay taxes on the fake fee. Martz, through Jones, would pass the rest to the presidential election committee.

In return for its contribution, Singer would insure help in securing government contracts. This was described by prosecutor Barnet D. Skolnik as "government favoritism to those able and willing to pay for it." Matz has admitted making payoffs to Agnew and Dale Anderson, former Baltimore County executive convicted of extortion.

During today's sentencing, Skolnik, who has led a team of prosecutors throughout the federal government investigation of Maryland political corruption, said Jones was a "third-party beneficiary" to Agnew's plea of no contest in October, 1973. Without the former Vice President's plea. "Mr. Jones would have been indicted in the fall of 1973."

Many participants in the Agnew prosecution provided testimony in exchange for various forms of immunity, a fact Agnew has cited bitterly as he claims his innocence. Others - including several engineers - have served jail terms for their role in the scandal.

Jones has denied any wrongdoing in connection with the kickback system and did not make any agreements to help prosecutors.

Jones, 56, who once headed the Chesapeake National Bank in Annapolis, was one of Agnew's closest friends and supporters when Agnew was governor of Maryland. He expanded his influence beyond Maryland when Agnew became Vice President and use it, according to prosecutors, to help procure government contracts for contributors.

Jones' sentencing was rescheduled from last week after the letter written March 28 by Jones irritated Watkins, who said he found no admission in the letter that Jones had solicited the Singer contribution as had been implicit in the guilty plea. Jones was given time to explain his first letter and compose a substitute.

In the March 28 letter, which Jones described as the "full truth of the case," he explained he did "not conspire with the Singer officials or anyone else to funnel this illegal corporate contribution" through Matz. He also claimed he made no suggestions to the company about present or future benefits if the contribution were made.

It was this tone that angered Watkins, causing him to reconsider his earlier acceptance of Jones' guilty plea. The judge admitted Jones' substitute letter "acknowledged that maybe he did do something wrong." He also agreed with Jones' attorney, Plato Cacheris, that Jones had been punished with the publicity, tension and strain on his family over the case. But the judge added, "He has been punished, I'm not sure that's enough."