Thomas C. Pulliam Jr., the former Prince George's County bank officer charged with receiving part of a $25,000 loan he made in the name of a fictitious person, denied under oath today that he participated in a scheme to secretly divert bank funds into a private business venture.

Testifying at his trial in federal court here, Pulliam, the former executive vice president of Jefferson Bank and Trust Co., also said he was fully convinced at the time he made the $25,000 loan that the person obtaining the loan existed.

Pulliam, 37, is charged with conspiring with Gordon R. Butler, a private investigator, to fraudulently obtain the $25,000 loan in May 1981 by using a fictitious name, "Robert Baker," and with submitting false financial information to get the loan.

Butler, a longtime Pulliam friend who has become the government's chief witness against him, testified last week that Pulliam knew that "Robert Baker" did not exist at the time he made the loan. Butler said Pulliam was aware that "Robert Baker" was an alias that Butler had used for many years in his detective work.

But Pulliam testified today that he did not learn that Butler and "Baker" were the same person until he met with Butler on Sept. 21, 1981, four months after the loan had been made and after the bank had fired him.

"Gordon Butler at this point told me he was and always had been Robert Baker," Pulliam testified. "I was just beside myself. I didn't believe I was hearing him say it."

The government contends that Pulliam used $10,000 from the $25,000 loan and $12,000 from an earlier $15,000 Jefferson loan he made to Butler in Butler's real name to help finance Pulliam's half interest in a satellite television antenna business he was starting with another bank customer.

Jefferson, a small two-year-old bank in Capitol Heights, has among its stockholders several prominent Prince George's businessmen and politicians, including County Executive Lawrence Hogan, county Planning Board Chairman Charles A. Dukes Jr. and Washington Bullets General Manager Bob Ferry.

Today, county liquor board member Gerard F. Holcomb, who's also a Jefferson stockholder and close Hogan political ally, testified for Pulliam. "Tom Pulliam is a very competent banker," said Holcomb, president of a subsidiary of John Hanson Savings & Loan. Holcomb said that when he borrowed money from Jefferson he found Pulliam to be "very thorough."

Under cross examination by prosecutor James P. Ulwick, Holcomb acknowledged he ran a private lending business from his John Hanson office in which he loaned money at the rate of 104 percent interest a year.

Responding to an objection from Pulliam's attorney, U.S. District Court Judge Joseph C. Howard told the jury not to consider Holcomb's testimony about the private lending business.

Outside the courtroom Holcomb told a reporter: "I'm here because the defense asked me. They subpoenaed me."

Holcomb told the reporter he is no longer making such loans which, in interviews with the Post earlier this year, he had said were proper.

In his testimony, Pulliam said when he received the $10,000 from Butler in May 1981, he had no knowledge that the money had come from the $25,000 "Robert Baker" loan. He said Butler gave him the $10,000 to invest in the satellite antenna business because Butler was joining him as a third partner in the new business. Butler did not tell him where he got the $10,000, Pulliam said.

"I had money that I could have invested myself," Pulliam said, but "Butler wanted to get in on the venture."

The $12,000 he invested in the satellite business a month earlier, on April 1, 1981, Pulliam testified, came from money he won at a Las Vegas casino. On his way back from Las Vegas, Pulliam said, he gave the money to Butler, who accompanied him on the trip, to hold for safekeeping.

Bank records show that Pulliam approved the earlier $15,000 loan to Butler on April 1, 1981 -- the same day that Pulliam made his first investment of $12,000 in the satellite antenna business.

The fact that his investments in the satellite business came at about the same time he approved the Butler and "Baker" loans was a "coincidence," Pulliam testified.

The government also contends that Pulliam and Butler prepared a phony financial statement showing that "Baker" had a net worth of about $300,000, which was used as the basis for granting a $25,000 unsecured loan to "Baker." Bank officials have testified that months later when they examined the loan and attempted to check the information included on the "Baker" financial statement filed with Jefferson, nothing could be verified.

Pulliam testified today that he did not attempt to verify the statement largely because Butler, who had always been a good bank customer, vouched for Baker.

Pulliam testified that he made two loans of $3,500 and $4,800 each to "Robert Baker" in 1978 and 1979 when Pulliam was a loan officer at another bank, the Bank of Bethesda. Both Bank of Bethesda loans had been paid off properly, Pulliam said.

Pulliam testified that during the course of making three separate loans to "Baker," he met him only once. "To the best of my recollection at some point, probably when I was at the Bank of Bethesda, I met someone representing himself to be 'Robert Baker,' " Pulliam said.

Pulliam also denied an allegation made by Butler in testimony last Friday that the $4,800 Bank of Bethesda loan had gone to Pulliam. Butler testifed that Pulliam approved both the Bethesda bank loans to "Robert Baker" to help Butler establish a financial "cover" for his private investigator's job.

Butler testified he turned the $4,800 over to Pulliam, and that he believes Pulliam used the money in the purchase of a house.