Prime Minister Shigeru Ishiba dissolved Japan's lower house of parliament on Wednesday to set up an October 27 early election and seek the voters’ mandate for his nine-day-old government.

Ishiba took office last week as Fumio Kishida resigned after three years leading the governing Liberal Democratic Party as it was dogged by corruption scandals.

With the early election, Ishiba is seeking to secure his governing party a house majority while he is still fresh and before the congratulatory mood fades.

The move has been criticised as prioritising an election rather than policies and for allowing little debate.

But Japan's opposition has remained too fractured to push the governing party out of power.

Ishiba announced his plans for an election even before he won the party leadership vote and became prime minister. His cabinet planned later on Wednesday to formally announce the election date and the start of campaigning next Tuesday.

Ishiba and his cabinet will stay in office until they win the election and are reappointed.

The speaker of the house, Fukushiro Nukaga, announced the dissolution of the lower, more powerful of the two parliamentary chambers at a plenary session.

“We will act fairly and squarely in order to win the people’s endorsement for the current administration,” Ishiba told reporters.

“Even while the lower house is dissolved the Japanese government must fully function” in tackling national security, disaster response and deflation, he said.

“We will devote all our body and soul for the people.”

Opposition leaders have criticised the prime minister for rushing to hold an election, allowing only three days of parliamentary debate on his policies and before achieving any results.

Even though opposition parties are too fractured to topple the governing party's almost uninterrupted postwar rule, the first public support ratings for Ishiba as prime minister were around 50 percent or even lower, the lowest levels for a new leader, according to Japanese media.

Ishiba is increasingly seen as backpedaling on a number of proposals he previously advocated so he won’t create controversy ahead of the election.

In his first policy speech at parliament Friday, he did not touch on his goal of establishing a stronger regional military framework and a more equal Japan-US security alliance, a dual surname option for married couples, and other issues seen as controversial or opposed by conservatives within the governing party.

Ishiba is unaffiliated with factions led and controlled by party heavyweights, which some experts say could make his tenure as party leader unstable.

None of his cabinet ministers is from the late Shinzo Abe’s faction that has been linked to damaging misconduct.

He also plans to not endorse some members of the Abe faction in the upcoming election to show his determination for cleaner politics.

Opponents have said that’s still too lax, but Ishiba is getting backlash within the party for being too strict. (AP)