Paritsan party politics long ago robbed the upper house of the Japanese Parliament of its reputation as "the house of conscience."

Shrunken in prestige and relevance, the House of Councillors is currently enjoying a return to the limelight because a July 10 election is widely expected to end 22 years of single-party rule in Japan.

Campaigning started today, and the conservative Liberal Democratic Party is desperately fighting for the 65 seats it needs to maintain a precarious parliamentary majority. Most observers believe that feat impossible, and early opinion polls do not give the corruption-tainted conservatives much chance of halting their slide in popularity.

Five major parties and a host of splinter parties and special-interest groups will contest the 126 seats in a legislative body patterned after the U.S. Senate but lacking most of its powers. The 252 councillors serve six-year terms, and half come up for re-election every third year.

Normally upper house campaigns lack the excitement of elections for lower house. Interest levels are high this year, however, because Japan appears poised on the brink of a political transition. Years of decline have taken their toll of the liberal Democratic Party, which has ruled Japan with support from big business and rural and middle classes since 1955. Between the elections of 1963 and 1976 the party's share of the popular vote fell from 55 per cent to 42.

If the pattern continues, the party will lose its majority in the upper house, which holds veto power over all legislation except budget and treaty bills. Japan does not, however, face a serious left-right division of political power on the lines of Italy or France, so the election results are unlikely to shake the country's overall stability.

"We will have enough seats to maintain our rule," predicted Liberal-Democratic secretary-general Masayoshi Ohira. "So far as I can see - and I don't mean 1,000 or 10,000 years - there will be no opposition government in this country."

Analysis concur that the conservatives may easily obtain support among moderate opposition parties without a formal coalition.

Although the continuation of conservative rule appears inevitable, a transition is under way in Japanese politics, and both the LDP and its principal opponent, the Japan Socialist Party face difficult elections. Public dissatisfaction with the two major parties has spurred the growth of smaller rival parties and spawned new challengers for the 40 per cent of voters who are uncommitted.

The Liberal Democratic Partu is being attacked on its flank by charismatic politician Yohei Kono and his guerrilla conservative group that seceded from the parent party last year. Kono's New Liberal Club captured a phenomenal 18 seats in the last general election and is expected to win another six seats this time.

The socialists - long plagued by internal warfare between left-wing Marxists and right-wing moderates - also face ballots-box challenge from reformists such as the fledgling Socialist Citizens' League.

Other minor contenders are the Japan Women's Party, which seeks to establish "female supremacy in this country of male chauvinism"; the United Progressive Liberals, a group of artists, journalists and educators who want to nurture grass-roots democracy; and the people's Society for New Solidarity, which is trying to weld more than a thousand diverse environmental and consumer groups into a single party.

Of the established parties, the Buddhist-backed Komeito and the middle-of-the-road Democratic Socialist parties are expected to benefit from a continuing centrist surge.

Candidates and journalists are having a hard time finding solid campaign issues, Japan has always had political parties with radical names, and Socialists and Communists are broadly supported and well-represented in the Diet [Parliament], but the radical policies they espouse are more rhetoric than reality.

Since the oil shortage forced Japan to abandon high growth, the country's fundamental conservatism has asserted itself in a marked rightward drift in domestic politics. The anti-Americanism once fashionable among the parties of the left is not heard and opposition to the Japan-U.S. security treaty - once the main element of political opposition - is now just an embarrassing skeleton in the discarded-policies closet.

When the Soviet Union conducted hard-nosed fishery negotiations recently, a wave of nationalism united the Japanese, and the Japan Community Party was no less vocal than anyone else in sniping at Moscow. A loading Liberal Democratic politician believes that a truly radical government is so inimical to Japanese character as to be inconceivable.

"If the Communists were to win an election here, they would turn into Japan, Inc., the next day," he said.