Trucking company president Masazumi Ando said he was furious when he saw the head of an investment firm that lost $1.3 billion in pension money bow in apology at a parliamentary hearing last week.

"This is nothing but a fraud," said Ando, whose 300 employees belong to a trucking-sector pension plan with $120 million in retirement savings that may now be gone for good.

"We are preparing to file lawsuits so that any cash that may be hidden overseas could be recovered," he told AFP.

Ando's sentiment may be widely shared amid the fallout from Japan's latest financial scandal, which has shaken trust in cherished private pension plans seen as crucial for millions in a country with a rapidly ageing population.

It also comes at a time when camera maker Olympus attempts to rebuild its own reputation following a $1.7 billion loss scandal by present and former top executives.

The problem at AIJ Investment Advisors goes beyond a cover-up -- analysts say the AIJ meltdown points to a serious problem with the deregulation of Japan's private pensions.

It also casts doubt on the future of small and medium-sized businesses if they cannot compensate about 880,000 employees who lost money in the scandal.

"Many of them are small businesses. They could collapse in a domino effect," said Hiroyuki Ozaki, a business professor at Tokyo University of Technology.

The spectre of such a collapse comes as Japanese firms, big and small, are already struggling to recover after last year's earthquake-tsunami disaster.

The stress is particularly acute for smaller firms that contribute more and more money to their pension plans, which tend to be generous in addition to Japan's national retirement scheme.

The fate of 109.2 billion yen ($1.3 billion) managed by AIJ was all but confirmed when president Kazuhiko Asakawa on Tuesday admitted wrongdoing, saying the company falsified its accounts to hide massive losses.

Asakawa told a parliamentary panel the money had disappeared in a string of risky bets on futures and options contracts between 2002 and 2011, but insisted he had not deceived clients since his plan included making the money back.

"I didn't want to use inflated figures for the pensions fund, but I did not want to come back with losses, no matter what," he told the panel in his first public appearance since the scandal surfaced in February.

"I was confident of recouping the losses," he added.

Regulators have so far found just 8.1 billion yen in accounts in Japan and Hong Kong, with one official saying some of the money may have been funnelled into offshore bank accounts, which Asakawa has denied.

His parliamentary appearance followed a raid on AIJ's Tokyo headquarters by securities regulators, which itself came after a January inspection of AIJ's books found it could not account for most of the funds under its management.

The Financial Services Agency halted the company's operations in February and then revoked its license as an asset manager in March.

No charges have yet been laid, but Mario Takeno, head of the Securities and Exchange Surveillance Commission, has said the watchdog may ask prosecutors to pursue criminal charges.

It has also been widely reported that former employees at the now-defunct Social Insurance Agency were hired at AIJ.

In 2007, the state agency that managed the public pension system admitted it could not find records for about 50 million accounts. The ensuing scandal contributed to the 2009 downfall of the long-ruling Liberal Democractic Party.

Yasuyoshi Masuda, a Tokyo University economics professor, said the wider problem was rooted in deregulation of the sector after Japan's booming economy headed south in the 1990s.

Authorities pushed for wide-ranging changes to stimulate the economy, easing rules for investment advisors looking to manage corporate pensions, he said.

"But following the deregulation, authorities failed to set up a system to impose penalties on almost fraudulent managers like this," Masuda told AFP, referring to AIJ.

"There is a flaw in the whole system," he said.