While debate continues in Japan on whether to amend the pacifist Constitution, less attention has been given to the referendum system under which the public will give its final say.

If such a vote is held, it will be Japan's first-ever national plebiscite on any topic. But critics say that, without addressing at least some of what they see as flaws in the constitutional referendum law, the historic event could leave a bitter aftertaste.

One contentious point of the law, enacted in 2007, is whether it ensures a level playing field in use of advertising, with the only notable regulation being a ban on paid TV and radio ads for the two weeks prior to the vote.

Masaki Miyamoto, a 44-year-old movie director, said he hardly turned his mind to the referendum procedures when making his film "Article 9" several years ago, which depicted young people clashing over whether to revise the war-renouncing article of the supreme law.

But he came to feel the need for an outright ban on TV ads throughout the whole referendum campaign after he began studying the law about a year and a half ago as a member of a civic group led by Hajime Imai, a journalist and referendum expert.

"As a filmmaker who knows how strongly video footage can influence us, I'm most disturbed that TV ads are banned only for 14 days," Miyamoto said, noting that the rules still allow wealthy groups to flood airwaves with ads in favor of their views during most of the expected campaigning period of 60 to 180 days.

"Some politicians may say we should think about changing the rules after trying (the referendum) once. But it's important that the first plebiscite is conducted at a high level of quality and in a fair manner," he said.

Japan's constitutional referendum law was enacted in May 2007 when Prime Minister Shinzo Abe, then in his first stint as the country's leader, sought to lay the groundwork for the first-ever amendment of the Constitution, which was enacted in 1947.

The law has since faced criticism, with a House of Councilllors panel citing in a resolution a number of issues that required further consideration, including advertising and the minimum voter turnout threshold.

Nevertheless, no substantial progress had been seen over the past 10 years toward revisiting campaign advertising rules, prompting members of the civic group to lobby for tougher regulations and to seek ways to raise public awareness over the issue.

Miyamoto is now working with Imai to make a documentary film on a two-day mock national referendum event organized on Thursday and Friday, bringing together around a dozen of people to debate and cast their votes over a set of prepared Article 9 amendment proposals.

"We hope to draw attention to both the discussions on Article 9 and the constitutional referendum law," Miyamoto said. "Just getting people to know that a national referendum may be held is the first step (to notice problems in the law)."

Another member of the civic group, Ryu Homma, a former worker at ad agency Hakuhodo Inc., released a booklet last September highlighting the huge cost of effective TV ads and the advantages one side could enjoy under what he calls Japan's "unique" advertising industry structure, in which one company holds a sweeping dominance over various advertising vehicles.

According to Homma, a 15-second TV ad spot during prime time can cost several million yen. The budget may balloon to hundreds of millions of yen to run a TV commercial in Japan's five major metropolitan areas for two weeks -- the level of exposure seen as necessary to ensure public recognition.

The writer also said campaigners who tie up with the more powerful ad agency will likely have greater access to certain prime-time TV spots and other media advertising slots, leaving campaigners on the other side with "leftover" slots with fewer viewers.

Some members are also concerned that TV spot advertising tends to appeal to emotions rather than logic, and thus will not help the public to engage in a rational debate over an issue that will decide the future shape of the country.

But it remains to be seen whether the efforts by the civic group members will make headway in time. A referendum may be looming within a year or so as Abe's ruling Liberal Democratic Party is gearing up to work out its amendment proposals by late March.

Abe has taken a cautious stance about revising the referendum law, saying at a Diet plenary session on Jan. 25 that the "conclusion" at the time of the law's enactment was to impose "minimum necessary" regulations to ensure fair campaign advertising.

Meanwhile, the Constitutional Democratic Party of Japan, the largest opposition force in the House of Representatives, has said it will work toward crafting a bill to revise the referendum law featuring tougher regulations on campaign advertising.

Even if Japan leans toward introducing tougher rules, how to strike a balance between freedom of expression and fair campaigning will require careful discussion.

Countries like Britain, whose 2016 vote on its membership of the European Union grabbed global attention, as well as France and Switzerland prohibit paid TV and radio ads in referendum campaigning, while the United States takes a minimalist approach in regulating political ads, according to a study by Japan's National Diet Library.

Yasuhiko Tajima, a Sophia University professor specializing in media theory, said he is against setting an outright ban on broadcast advertising, given that ads are "a crucial part" of freedom of expression.

But he recognizes the need to address undue unfairness due to differences in financial resources.

"I don't think pouring in money will necessarily ensure victory -- in other words, voters shouldn't be viewed too much as people who can be made fools of (by being easily swayed by manipulative ads). But being well-financed is undeniably an advantage and we may need something like a spending limit to ensure a fair contest," the professor said.