TOKYO, Japan: Toyota's chairman, Akio Toyoda, faces backlash from shareholders this week as major proxy groups push for a vote against him remaining on the board.

This comes after Toyota recently apologized for fraudulent vehicle certification tests, a significant blow to the automaker's reputation for quality.

The June 18 annual shareholders meeting will see this critical vote following Toyota's suspension of production for three models due to the scandal. Despite these issues not involving safety problems, the company's market value has dropped by about 3 trillion Japanese yen (US$18 billion).

Institutional Shareholder Services (ISS) has called for Toyoda to be held accountable, noting that his promises for change did not include a board reshuffle. ISS argues that the company's efforts to preserve its corporate culture may have contributed to recurring testing issues.

"The company's propensity to preserve its corporate culture is in fact suspected, and Toyoda should be held accountable for that," it said.

Another significant shareholder, Glass Lewis & Co., has also recommended voting against Toyoda and executive Shigeru Hayakawa. They cited Toyoda's failure to ensure proper internal controls and governance at group companies. Both ISS and Glass Lewis are not opposing other board members, including CEO Koji Sato.

The past year has seen multiple scandals involving improper vehicle checks at group companies such as Daihatsu Motor Co., Hino Motors, and Toyota Industries Corp. Similar issues have been found at Honda, Mazda, and Suzuki.

Glass Lewis has also advised against a proposal to lobby for climate change, calling for more transparency. They stressed the need for more independent board members and improved governance.

Despite these challenges, Toyoda is unlikely to be ousted, as major shareholders like Japanese banks and financial institutions holding significant shares are not expected to challenge him. Last year, Toyoda was re-elected with nearly 85 percent of the vote.

Toyota's recent performance has been strong, with profits doubling to 4.9 trillion yen ($31.9 billion) in the fiscal year ending March, driven by increased vehicle sales and a weak yen boosting overseas earnings. The company, the world's leading automaker, sold 9.4 million vehicles in the last fiscal year.

Analysts like Aaron Ho of CFRA Research believe that the recent scandal will only have a minor impact on Toyota, noting that production halts are likely temporary and do not reflect deeper issues within the company.

In his apology, Toyoda referenced his handling of a massive recall scandal in the U.S. in 2009 over "unintended acceleration," suggesting that Toyota has faced and overcome significant challenges before.

"We are not a perfect company. But if we see anything wrong, we will take a step back and keep trying to correct it," Toyoda said.