Richard Nixon on television tonight contradicts testimony of his friend and banker, Charles G. (Bebe) Rebozo, about the controversial campaign contributions of Howard Hughes, the eccentric billionaire.

Nixon, in the fourth of his TV interviews with David Frost, concedes he offered to use political campaign funds controlled by Rebozo to defray legal expenses of his key aides, H.R. Haldeman and John Ehrlichman.

When testifying before the Senate Watergate committee, Rebozo was asked about the Hughes cash contributions. Rebozo said Nixon told him in March, 1973, as the Watergate scandal began to engulf the President and his aides, that he must return the Hughes money. Rebozo also recalled that Nixon said it would have been wrong to use that money because it constituted campaign contributions.

Tonight, Nixon offers a different version.

A full month later, in April, he asked Haldeman and Ehrlichman to resign because of their Watergate involment. Frost brings up that period, and then asks the former President about the "very generous offer you made" to use the $300,000 for lawyer's fees from a fund that Rebozo had. When Frost asks Nixon what he had in mind, Nixon replies:

"Well, as a matter of fact, I had in mind the campaign contribution that he received from Hughes . . ."

That incident forms one of many controversial episodes that Nixon addresses in the fourth interview, which covers the overthrow of the Allende regime in Chile, the resignation of Vice President Spiro Agnew, the events surrounding his final days in office and his acceptance of a pardon after his own resignation.

In tonight's program, Nixon makes a number of new assertions.

On the Agnew case: Nixon says that Elliot Richardson, then the Attorney General, and Henry Petersen, in charge of the Justice Department's Criminal Division, both "strongly" said they would recommend a prison term for Agnew. Nixon takes a swipe at Richardson by saying "he was under considerabel strain at that time because of his political ambitions."

On the final days: Nixon confirms many of the details previously reported in the book by Bob Woodward and Carl Bernstein, such as crying and praying alone with Henry Kissinger on the night before his resignation.

But he implies the reporters' book may have contributed to Mrs. Nixon's stroke. "All I can say is Mrs. Nixon read it, and her stroke came three days later," he says. He also describes the reporters as "trash," and adds: "I will never forgive them, Never."

On his pardon: He says he accepted President Ford's pardon after weighing all the consequences. A key factor in his mind, he says, was the advice of his lawyer, Herbert J. Miller. He quotes Miller as telling him "there was no chance whatever I could get a fair trial.

Tonight's program is at 7:30 p.m. on Channel 5.