The huge sign hanging over the opulent ballroom in the Okura Hotel declared: "Meeting to encourage Mr. Kondo." Tetsuo Kondo, an aspiring Japanese politician, had every reason to feel encouraged.

The corporate elite was present for his elaborate feast. The man from Mitsubishi was there. The head of Nippon Steel gave a speech of lavish praise. A founder of Sony had signed the invitation. Sipping sake and scotch and dining on turkey, roast beef and Japanese delicacies, more than 2,000 guests representing the cream of the business world was there.

They had paid 10,000 yen ( $47) and more in company money to cheer up Kondo - and to help fill his coffers for an election campaign this fall. The next day, no one could say how much was taken in. Kondo aides said they plan to report it all, but not until next March, long after the election.

This loose flow of corporate cash to politicians - and the politicians unblushing solicitation of it - is typical in Japan where controls on political contributions are foggy and accountability is often ignored in a fashion that makes the much criticized American standard seem a model of rectitude by comparison.

Legal spending limits are winked at. Each candidate in parliament's lower house election, expected this fall, is supposed to spend no more than 20 million to 30 million yen ($93,000 to $140,000), depending on the size of the constituency.

But Kiyoshi Hanada, chief of the secretariat of the Liberal Democratic Party, candidly concedes: "Actually, the minimum spent is about double that which is allowed and some even spend up to 150 million yen ($698,000)."

The Liberal Democrats are the major beneficiaries and an aura of scandal has hung over them ever since they consolidated power in the 1950s. It began in 1954 when the shipbuilding industry was accused of getting tax subsidy favors after making political donations to the right people. Former prime minister Kakuel Tanaka is now on trial on charges he took a 500 million yen bribe in 1972 from the Japanese agent of Lockheed. Another Liberal Democrat stalwart, Raizo Matsuno, resigned his seat recently under a cloud of suspicion that he accepted 500 million yen from the agent of another American plane manufacturer.

But many Japanese critics of what is called "money politics" worry less about such highly publicized scandals than they do about the routine flow of corporate money to many conservative politicians each year, much of which is technically legal under current law. These critics claim it is built-in influence-buying by business giants and refer to the whole system as "structural corruption."

"The political money system threatens the democratic system," says Naoki Kobayashi, a law professor at Tokyo University and leader of a group calling for reform. It is impossible to check up on reported corporate donations, he says, adding, "This is a law with many loopholes." Kobayashi's group urges that all donations from business, labor unions and other organizations be banned and that campaign financing be limited to private individuals.

A government report issued Staurday showed that the Liberal Democratic Party has a total income of 11.1 billion yen ( $51 million) in 1978 and that 10 percent of it came from private donations, chiefly business firms. No one can estimate how many disguised corporate contributions go unreported.

A company legally is limited to gifts of 100 million yen ($465,000). But sources knowledgeable about campaign contributions say that a large corporation may give as much as 500 million or a billion yen ($2.3 or $4.7 million) to parties, groups and individual politicians.

The law was tightened in 1976 after the Tanaka scandal and established limits that liberal Democrats say are unrealistic. They get around it by various subterfuges, including the following:

"Enocuragement parties," such as Knodo's, to which large corporations are invited, with the unstated expectation that each guest will have paid about 10,000 ro 20,000 yen. Companies transfer the payments directly through bank accounts and send lower-level employes to do the drinking and eating.

Parties and important politicians publish their own newspapers and charge high rates for corporate advertisers. One published in July by the Liberal Democrats carried ads from camera steel, electronics, construction and oil companies.

Politicians take 100,000 yen fees for giving company "lectures," to which only a couple of low-ranking employes are assigned to form an audience.

Corporations pick up politicians' bills at Tokyo's geisha restaurants where the tab for a night's revelry may run into the hundreds of dollars.

The subterfuges are widely known and chuckled at. The critics who object are grandly ignored. Recently, however, there has been a rising chorus of criticism directed at the Liberal Democratic Party, which is reportedly considering revising the law to make even more corporate money available. A leading newspaper, the Asahi, denounced t e plan as an "insolent move" and pronounced itself "flabbergasted." Former prime minister Takeo Miki has proposed banning all but private donations.

Such reformist notions disturb the Liberal Democratic leaders who depend heavily on corporate largesse. The Socialist and Communist parties get their funds mostly from memberships and party newspaper subscriptions. Cutting off company money to the Liberal Democrats would be a serious blow.

"As a practical matter, the LDP gets its money from corporations," says the party's secretariat chief Hanada. "All Japanese understand that. But individual Japanese don't like to pay money to politicians."

One of the party's thoughtful young politicians, Junichiro Koizumi, says many in the party already suffer a fund shortage as a result of the limits imposed in 1976 and are resorting to the ballroom parties where contributions run about 10,000 or 20,000 yen each.

That is better than the old system, Koizumi thinks, because it means the politician no longer relies on a few huge contributions from big business.

"The amount we get from any one person now is small," he says. "This makes me free. I am not subject to the influence of only one big business.

During 1975, when the post-Tanaka reform law was being debated, there was a strong feeling that all corporate donations were evil, Koizumi recalls. "Now we no longer feel that way. We feel it is impossible to run our political parties without corporation money." CAPTION: Picture, TAKEO MIKI...favors banning some donations