(Adds detail, background.) LONDON (Dow Jones)--An investor group is calling for a revamp of Vodafone Group PLC's (VOD) board due to concerns about the mobile giant's strategy and track record on acquisitions. Ontario Teachers' Pension Plan, or OTPP, which holds a 0.42% stake in the world's biggest mobile-network operator, plans to vote against the re-election of non-executive Chairman John Bond and Deputy Chairman John Buchanan at its annual shareholder meeting July 27. "For at least the last five years, the company has had significant structural and strategic weaknesses, resulting in Vodafone trading at a substantial, persistent discount to its asset value," OTPP said on its website. "Having engaged with management and certain members of the board, Ontario Teachers' believes that board rejuvenation is a critical step to catalyze a corporate restructuring and a re-examination of Vodafone's long history of poor capital allocation and disastrous M&A," it said. However, OTPP will vote for the re-election of Chief Executive Vittorio Colao, who took the helm in July 2008, as he has started to improve Vodafone's operating performance and competitiveness. A Vodafone spokesman said the company doesn't comment on individual shareholders' views, but noted that it maintains "a regular and open dialogue with them." "The board's primary purpose is to deliver shareholder value and we have continued to deliver a very strong financial performance," he added. Still, Vodafone recently booked a GBP2.3 billion impairment charge on its India operations due to competition and a fierce price war. Investors are also restless about Vodafone's investment in Verizon Wireless, its U.S. joint venture with Verizon Communications Inc. (VZ), which hasn't paid a dividend since 2006. In November, Colao said resolving that issue was the group's top priority. Over the past two years, Calao has turned his attention to cash generation and shareholder returns by developing the U.K.-based group's high-growth operations in Asia, Africa and central Europe. He has also halted the company's expansion in emerging markets such as India and Turkey, a key strategy of former CEO Arun Sarin. Vodafone is expected on Friday to report a 0.1% fall in underlying service revenue to GBP10.39 billion for the first quarter ended June 30 from a year earlier following a slight improvement in the previous quarter, underpinned by growth in mobile data and fixed broadband. -By Lilly Vitorovich, Dow Jones Newswires; 44-0-207 842 9290; lilly.vitorovich@dowjones.com (END) Dow Jones Newswires July 21, 2010 09:37 ET (13:37 GMT)