SEOUL (Reuters) - Worries that Hyundai Motor Group's planned restructuring will benefit the controlling family ahead of some shareholders have hit Hyundai Mobis Co Ltd 012330.KS, which is set to be the group's de facto holding firm, sending its shares sharply lower on Thursday.

A Hyundai Motor's booth is seen near the Pyeongchang Olympic Plaza in Pyeongchang, South Korea, February 11, 2018. REUTERS/Kim Hong-Ji

The parts supplier's shares fell 3 percent as investors fretted it may be forced to hand over a lucrative business to Hyundai Glovis 086280.KS, another group firm, too cheaply as part of the structural overhaul. At one point, it tumbled as low as 8 percent.

“From the perspective of the biggest shareholders, this is a satisfying deal...but for minority shareholders, there seems to be nothing for now,” said Lee Hae-chang, a portfolio manager at Franklin Templeton Investment Trust Management.

Lee, who attended an investor conference held by executives of both Mobis and Glovis, was one of many participants questioning whether the deal will be beneficial to smaller Mobis investors.

Hyundai Motor Group, South Korea’s second-biggest family-owned conglomerate, said on Wednesday it planned to streamline its complex ownership structure in response to pressure from the government and investors.

The chief of South Korea’s antitrust agency, Kim Sang-jo, said the plan was a “positive” step towards improving the group’s ownership structure.

Under the plan, which needs the approval of both companies’ shareholders on May 29, Hyundai Mobis will spin off its domestic module and after-service parts businesses and merge them with Glovis, a logistics firm.

Hyundai Motor Group chairman Chung Mong-koo and his son and vice chairman Chung Eui-sun plan to sell their shares in Glovis to buy stakes in Mobis. Affiliates Kia Motors 000270.KS, Glovis and Hyundai Steel 004020.KS will sell their stakes in Mobis as part of the exchange.

Hyundai Glovis shares closed up 4.9 percent, having earlier surged as much as 23.6 percent to their highest intraday level since Oct. 2015.

At least one fund manager said he would be opposing the deal.

“This is passing too big a piece to Glovis,” the fund manager told Reuters ahead of the investor conference, declining to be identified as he was not authorized to speak to media.

Park In-woo, an analyst at Mirae Asset Daewoo, said that while the valuation for the after-service parts business seemed a bit low, the mid-to-long term view for Mobis was positive.

“After the spin-off and merger, Hyundai Mobis will be on the top of the group’s ownership structure and will be able to expect effects such as boosted shareholder returns,” Park added.

In addition to resolving the group’s cross-shareholdings in response to regulatory pressure, the restructuring plan also paves the way to building up capital for the junior Chung to ultimately gain control of the group, investors and analysts said.

The domestic after-service parts business that will pass from Mobis to Glovis is a stable cash cow, and without it Mobis could find it hard to fund future tech development, said Lee Jae-il, an analyst from Eugene Investment & Securities.

Other major group affiliates lost ground, with Hyundai Motor falling 5.3 percent and Kia Motors down 3.5 percent as investors were disappointed that these companies weren’t included in the planned restructuring, Shinhan Investment Corp analyst Jung Yong-jin said.