A group of influential Japanese politicians views the longstanding relationship between White House national security adviser Richard V. Allen and Tamotsu Takase, a business consultant, as an important backstage link in its contacts with the Washington establishment, according to a leading Japanese member of parliament.

"The relationship between Allen and Takase," said Shintaro Ishihara, "is very precious." Ishihara belongs to the lower house of the Diet, or parliament, and is a protege of former prime minister Takeo Fukuda, who heads a powerful faction in the parliament.

Allen and Takase, he explained, have been instrumental in arranging meetings between establishment figures in the two countries in recent years. He said that the two men had a key role in setting up a meeting between Fukuda and President Reagan at the White House in March.

They have also provided over the years a flow of information on political trends in the United States, he said. That flow has continued, he said, since Allen took office in January, with Takase acting as the go-between.

The "pipeline" between Allen and Takase, as such relationships are referred to in Japanese political and business circles, reflects a Japanese tradition of using intermediaries to oil the wheels of dealings among prominent business and political figures who generally shun direct involvement to avoid a possible loss of face.

While White House contacts this year between Allen and Takase, one of the chief Japanese business contacts of Allen's former consulting firm, have brought into question in the United States the nature of the two friends' current relationship, the Japanese tend to view it as a normal extension of close personal ties.

Takase has told Japanese reporters that he asked Allen's help in arranging the controversial Japanese magazine interview with Nancy Reagan on Jan. 21 in which his wife, Chizuko, took part.

Allen acknowledged that he has had as many as four meetings in the White House with Takase, including one in March in which Takase accompanied a top Japanese autombile executive to discuss, among other things, Reagan administration attitudes on trade. The administration was at the time involved in sensitive negotiations with the Japanese on import quotas for Japanese cars.

In a recent interview in his Tokyo office, Ishihara said that Allen, whom he first met about 10 years ago on Takase's introduction, has been a frequent source of information on political trends in Congress and the executive branch.

In exchange for Allen's briefings, which have normally been channeled through Takase or contained in letters directly from Allen, Ishihara has provided "background information" on developments within Japan's ruling Liberal Democratic Party on Allen's request.

In a telephone interview today, Ishihara said he has not had any direct contact with Allen through letters or in telephone conversations since Allen took office. But, he said, "We have kept in contact through Takase."

Takase has made several trips to Washington this year. Ishihara said that "on Takase's return home, I met with him and heard Allen's views on American politics. These did not include any kind of state secrets."

Ishihara said he had direct contact with Allen in the days before Allen became White House security adviser. He said that since Allen took office the exchange of information has been limited to communications with Takase.

Ishihara said that Allen has continued to solicit his "personal views and analysis" of Japanese political trends through Takase, including attitudes among the Liberal Democrats on the controversial visit to Japan of Palestine Liberation Organization leader Yasser Arafat in October.

In the earlier interview, Ishihara stressed that no money has been involved in what he characterized as a normal and casual exchange of information. He would not elaborate on the nature of information exchanged.

Maintaining contacts with political figures in Japan would seem to fall within Allen's normal duties at the White House. For the Japanese, however, who often feel hampered by the lack of high-level personal ties with U.S. officials, such contacts take on major importance.

"Personal ties with people in Washington," said a political consultant who has often been used as a Japanese go-between, "are still sporadic at best. Japanese politicians go to Washington, but there are very few who can handle the language, and their meetings with Americans are very stiff and formal. Very few are capable of mingling effectively."

Allen, Ishihara said, "is a very ambitious, intelligent man and has had a lot of contact with Japanese companies and scholars. He is a rare American who understands Japan well."

In 1978, Ishihara recalled, he was asked by Takase on Allen's behalf to arrange a series of meetings with key Japanese political and business figures for Ronald Reagan who was visiting Japan. As a result, he arranged for Reagan to meet with then-prime minister Fukuda, he said.

In March, when Fukuda went to Washington as Prime Minister Zenko Suzuki's special representative, Ishihara asked Allen's help, again through Takase, to set up a meeting with President Reagan.

Asked why the arrangements for the meeting were not made through regular diplomatic channels, Ishihara said, "The Japanese Embassy in Washington is too busy with day-to-day diplomatic affairs and has no time to develop important political connections."

Such backdoor maneuvers reflect the Japanese tradition of nemawashi, or "root-binding," in which go-betweens are frequently used to lay the groundwork in arranging meetings or carrying out delicate negotiations.

A more direct approach to such matters might, as the Japanese tend to view it, invite a humiliating rejection. But once all the loose ends have been tied up by intermediaries, the principals can safely surface to put their final stamp of approval on the arrangements.

This unobtrusive style of doing business prompts Japanese political and business leaders to put a premium on individuals they believe to have key links with establishment figures in Washington.

"When someone like Takase comes along," said the political consultant, "there is the feeling here that he has to be the guy to do something effective."

Takase, 52, is a professor at Kyoto Industrial University and has a longstanding reputation as a go-between with the United States. According to academic and business colleagues, Takase has, over the year, stressed his close relationship with Allen and has used his university position to help enhance his business activities.

"Takase is essentially a greaser of wheels," said one business acquaintance, who did not want his name used. "He uses his contacts in business and the Japanese bureaucracy to make deals." Takase's financial stake in these activities remains hazy.

What is more clear, according to some of his colleagues, is that he has used his close ties with the Fukuda group in the Liberal Democratic Party to help promote his consultant work. He reportedly was introduced to influential party members in the 1960s by Okinori Kaya, who had been convicted as a class-A war criminal by American occupation forces for his role in Japan's wartime Cabinet.

Kaya made a political comeback in the early 1960s on a strongly pro-American, anticommunist platform, views still in vogue with Japanese right-wing politicians.

Takase, it is widely believed here, was used as a back channel go-between with Washington by the late prime minister Eisaku Sato in delicate negotiations over Japanese textile exports to the United States in 1969.

Takase met Allen in the 1960s when both men were working at the Hoover Institute at Stanford University. Despite the two men's list of shared contacts in Japanese business and political circles, their previous business relationship in Japan is obscure.

Today, Takase is on the payroll of Technova, a Tokyo-based consulting and research firm, as a senior director. Peter D. Hannaford, who bought Potomac International, Allen's former consulting firm in January, has said Potomac did some work for Technova before Allen became national security adviser.

In a telephone interview from his home in California, Hannaford said Saturday that according to records he has seen since buying Potomac International, the company did "some consulting" for Technova "two or more years ago." He said he did not know what the projects were about and declined to say how much Potomac was paid for them.

Shogo Toyoda, Technova president, said in a telephone interview that his firm did not have any working relationship with Allen.

Knowledgeable sources confirmed that Potomac had a contract, while Allen headed the firm, with the Industrial Research Institute (IRI) in Tokyo, an organization sponsored by the Japanese energy industry.

The contract, which was worth between $30,000 and $40,000 a year and called for supply of information on U.S. political developments relating to the energy and nuclear power industries, has recently been renegotiated with Hannaford, sources close to IRI said.

Hannaford confirmed that the contract had been renegotiated in the spring, but declined to give the amount. He said Potomac "does no work on political trends," but would "provide monitoring on energy and industrial trends and legislative trends" for IRI.

Allen could not be reached for comment on his relationship with Technova and IRI.

Takase has been a member of the board of the International Energy Forum (IEF), a research group belonging to IRI, since it was founded in April 1980. IEF occupies an office next door to Technova's computer-packed headquarters in a new high-rise office building in downtown Tokyo.

Technova's Toyoda said that his firm has recently retained Hannaford to handle public relations in the United States for a two-year study of the Japanese and American automobile industries.

The project is being carried out by Technova's staff of 11 researchers and the Center for Japanese Studies at the University of Michigan and is paid for by leading auto manufacturers in the two countries. It is Technova's first contract with Potomac, Toyoda said.