Arnaud de Borchgrave, a veteran foreign correspondent who coauthored a bestselling novel about Soviet influence on the American media, yesterday was named editor in chief of The Washington Times.

The dapper and perpetually tanned de Borchgrave takes over editorial control from Smith Hempstone, who was editor in chief for less than a year. Hempstone said he was in Madrid, on a tour of the newspaper's foreign bureaus, when a Times lawyer told him Monday he was being demoted to associate editor of the paper.

"They got the script wrong," said Hempstone, who took over last July when James Whelan was ousted as editor and publisher of the Times. "Usually when there's a coup, I win." Hempstone will continue to write a twice-weekly column.

Managing editor Woody West becomes executive editor, a post that has been vacant since Hempstone became editor in chief last year. Deputy managing editor Wesley Pruden becomes managing editor.

De Borchgrave, who in his 25 years at Newsweek became known as one of the world's most flamboyant and controversial correspondents, was already a member of the Times' editorial advisory board.

"At Newsweek, I specialized in major exclusives and scoops and exclusive interviews with world leaders," he said in a telephone interview yesterday. He added that he sees a "vacuum" for that kind of reporting in general, citing what he called the failure of the "liberal media" to cover such stories as Cuban government involvement in drug smuggling.

"Everywhere I go in this country there is a thirst for an alternative voice," he said.

However, he said he will not focus exclusively on strengthening the foreign coverage.

"We're a Washington paper," he said. "I plan to get involved at every level."

De Borchgrave said he was first approached about three weeks ago by Col. Bo Hi Pak, president of News World Communications Inc., an affiliate of the Rev. Sun Myung Moon's Unification Church, which owns the Times. He said Pak offered him the job of publisher, which he refused. Last weekend, he said, Pak offered the job of editor in chief, which de Borchgrave accepted.

De Borchgrave, who was fired from Newsweek in 1980 after an editorial dispute, was described as a "legend" in the Times' official announcement. Pak said in a release that de Borchgrave "knows the world intimately and has repeatedly broken new journalistic ground in his distinguished career."

Since leaving Newsweek, which is owned by The Washington Post Co., de Borchgrave has helped operate a newsletter called Early Warning, which he said is read by 23 heads of state and 16 directors of national intelligence agencies. He is also a senior associate at the Georgetown University Center for Strategic and International Studies.

But de Borchgrave acknowledged that he missed the impact of his Newsweek stories. "Every day of my life I've been in touch with major stories, and I'd be somewhat upset that I didn't have an outlet," he said.

The naming of de Borchgrave as editor in chief was met with applause from a number of conservatives who view the 58-year-old coauthor (with Robert Moss) of "The Spike" as a hardliner against communism and communist influence in the world.

Howard Phillips, director of the Conservative Caucus, said conservatives are "thrilled" by the move.

"If I were [Secretary of State] George Shultz, I would start biting my fingernails. He will no longer have a free ride in terms of his policy of unilateral deterrence, vis-a -vis the Soviet Union," Phillips said.

Some journalists who had worked with de Borchgrave or competed against him had a less sanguine view of how he would guide the paper.

Lars-Erik Nelson, Washington bureau chief of the New York Daily News and a former Newsweek colleague, said of de Borchgrave: "He's a very talented and courageous guy, but he seems to me to have gotten hung up on a philosophy that the KGB has become a dominant influence in American journalism through disinformation or suppression of vast numbers of stories about a communist plot."

The hiring of de Borchgrave comes at a crucial time for the three-year-old Times, which has gained influence among conservatives and is widely read by officials in the Reagan administration.

However, despite the more than $150 million that has been poured into the paper by Moon's church, it has failed to make significant circulation gains and is largely bereft of major advertising. Last year, after the paper launched a national edition, officials said it had an unaudited circulation of 95,000, with 65,000 in the Washington area.

Times officials yesterday declined to provide more current circulation figures, saying the results of an official circulation audit will be released in a few weeks.

"I don't want to be in a position of giving out figures that are confusing," said Phil Evans, the deputy general manager.

Last year's editorial upheaval brought charges of church intervention in the news operation. Whelan said last July that Pak had violated his promise of independence and that the Times had become what he called a "Moonie paper."

De Borchgrave said yesterday that he had been given a guarantee of "total independence . . . The Unification Church does not control the editorial product," he said.