A congressman who fell victim last month to the political muscle of the Christian right charged yesterday that the agenda for such groups as Jerry Falwell's Moral Majority has been set by Rep. Robert E. Bauman (R-Md.).

Rep. John H. Buchanan (R-Ala.) said Bauman, who was charged last week with soliciting sex from a 16-year-old boy, was the "undisputed leader . . . of the group that formed those issues that have become the 'Christian' issues" for Falwell and others of the emerging Christian right. Falwell, pastor of the Liberty Road Baptist Church in Lynchburg, Va., and Tv evangelist, has become one of the most outspoken leaders of this year's plunge by the far-right wing of evangelical Christians into politics.

Buchanan told a men's fellowship breakfast at the Twinbrook Baptist Church in Rockville that the political positions of groups such as the Moral Majority and the Christian Voice are "essentially the same as the issues of the American Conservative Union . . . the far-right extremist political positions are being clothed in robes of righteousness."

The Christian political right has never denied its ideological kinship with the American Conservative Union, of which Bauman is chairman. But Bauman's troubles, including the disclosure by FBI agents that he has been a frequent customer of homosexual bars, raises an interesting paradox, since opposition to homosexuality has been one of the bulwarks of right-wing Christian movements such as Falwell's. Much of his fund-raising is geared to antihomosexual appeals.

Bauman was permitted to plead innocent to the solicitation charge on the promise that he would enter a six-month rehabilitation program that includes treatment for alcoholism. A Bauman spokesman said the congressman would not comment on Buchanan's remarks.

Buchanan, a former Baptist preacher who is a 16-year veteran of the House of Representatives, was unexpectedly defeated last month in his race for renomination. He blames his defeat -- and political analysts agree -- on a massive campaign against him by Moral Majority. "They sent out letters saying I was un-Christian" because Buchanan's voting record on issues such as the establishment of the new Department of Education, the Panama Canal and on a trade embargo against the former White-dominated government of Rhodesia differed from the position of the American Conservative Union, the congressman said.

"They turned out 2,500 volunteers and went door to door, telling people not to vote for me," he said. Buchanan said that, based on polls taken earlier this year, 1980 "had been scheduled to be my best year."

But he was defeated by a 55-to-44 percent margin by Albert Lee Smith, an ultraconservative who was once active in the John Birch Society. The activity of the right-wing Christians "served to frustrate the will of the majority of the citizens in my district," he charged, adding that even after his primary defeat, "the polls show that I am the choice of the majority in my district."

Buchanan expects a decision today on his bid to get on the ballot in November as an independent.

The congressman defended the rights of Christians to engage in politics. "God expects us as Christian people to be concerned, to be informed, to be active, to be involved," he said. But to contend that there is only one "Christian" position on complex political issues is a violation of both the Christian and the democratic traditions, he said. "We need to be very careful about this confusing of political issues with what is moral and Christian," he said.

Buchanan said a delegation of right-wing Christians called on him last April at the time of the Washington for Jesus rally. "They said, 'We're here to tell you what the Christian position is,'" he recalled. He said they told him that "'on the issue of the Department of Education, the Christian position is to oppose the Department of Education.'" The former Baptist preacher said he was given similar instructions on a number of other issues.

He engaged in a lively Biblical discussion with his callers, he said, telling them that "the voice I hear is the burden 15 million people on earth who will die this year" because of hunger or other deprivation. "God has laid that burden on me," he told the visitors, citing scriptures of Jesus' challenge to his followers to care for the poor.

"They (the visitors) seemed to respond warmly at the time," Buchanan recalled, "then they went back home and beat my brains out."

Buchanan warned that Falwell and others of the Christian far right "are a much more potent development in American politics than many people realize." aHe added that "we can't forbid Jerry Falwell from doing what he is doing but it is time for a lot of other folks, other Christians, particularly evangelicals, to speak up."