A Laguna Beach private investment firm that is the fifth largest shareholder in U.S. Auto Parts Network Inc. said it wants to buy out the largest holder’s stake so it can better influence a turnaround of the Carson automotive e-commerce company.

Maguire Asset Management LLC said Wednesday that it wrote U.S. Auto Parts’ board this week to announce that it had approached Oak Investment Partners about acquiring that firm’s stake of the company, or about 28 percent.

Timothy Maguire, principal at Maguire Asset, noted that the company’s share price has plunged more than 90 percent since its 2007 IPO. He holds the company’s management and board responsible for most of that decline, and wants to see Chief Executive Shane Evangelist replaced and former Philadelphia Insurance Cos. Chief Executive Sean Sweeney added to the board in order to increase the number of independent directors.

Maguire Asset is a relatively recent investor in the company, having disclosed in a July regulatory filing that it had accumulated a 5.3 percent stake. Maguire said in his letter that he has been talking with management about the company’s strategic direction, and urged the board to examine strategic options that could include even the sale of the entire business.

“We continue to acquire shares of U.S. Auto Parts because we believe the company's stock price is extremely undervalued,” Maguire wrote. “The company is a market leader with an 11 percent market share and, most importantly, we believe the business has enormous potential for improvement.”

U.S. Auto Parts, with online operations that include USAutoParts.net, AutoMD.com and AutoPartsWarehouse.com, has been losing traffic to competing auto e-commerce sites and struggling to adjust to policy changes at online marketplace eBay. The company also had challenges integrating its 2011 acquisition of Chicago competitor Whitney Automotive, which it bought in a deal valued at $27.5 million.

Last month it reported a wider second-quarter loss and a 16 percent drop in sales despite efforts to cut operating costs and drive more consumer traffic to its sites.

U.S. Auto Parts has not yet commented on Maguire’s overtures. Its stock was one of the biggest movers Wednesday on the LABJ Stock Index, closing up 13 cents, or 12 percent, to $1.26 on the Nasdaq, then rising another 1.5 percent in after-hours trading.