Procter & Gamble Co. (PG - Get Report) shares were marked to open lower Monday, July 17, as it looks set to face a proxy battle from Nelson Peltz.

P&G shares were marked 0.25% lower in Monday premarket trading at $86.88. Shares closed at $87.10 on Friday, July 17.

Peltz's Trian Fund Management Monday said it had filed preliminary proxy statement with the Securities and Exchange Commission for the election of Peltz to the P&G board at the company's 2017 annual general meeting, saying that given P&G's disappointing results over the past decade, "Trian has a keen interest in helping the Company address the challenges it is facing."

The move, which will make P&G the largest company to face a proxy battle was first reported by the Wall Street Journal Monday citing people familiar.

Trian, which owns about $3.3 billion of P&G stock, said P&G has underperformed relative to its peers and the S&P 500 over the past decade, saying that total shareholder return was less than half that of its peers and has been in the bottom quartile over recent time frames. 

The activist investor said the consumer products giant needs to address its deteriorating market share, and its excessive cost and bureaucracy. 

P&G, Trian said, has to act with more urgency to address the market share it is losing to both its peers and smaller local competitors. Trian also says that P&G's $10 billion cost-cutting effort launched in 2012 has had no discernible impact of profits or sales growth. The investor also said that P&G has an overly complex organizational structure and a slow moving and insular culture.

Trian said that has been in talks with P&G over the past four months, but the company rejected to name Peltz as a director.

"As a member of the Board, it would be my goal to help improve performance by increasing sales and profits and regaining lost market share. I also believe the Board must address the company's structure and culture. I can add far more value operating within the P&G boardroom than by merely looking in from the outside," Peltz said in a statement. 

Trian pointed out that it was not advocating a break up of the company or suggesting that the CEO or directors should be replaced. It is also not advocating taking on excessive leverage, cutting pension benefits, or suggesting that research & development, marketing expense or capital expenditures be reduced.

Sales at P&G have stalled due to pricing pressure and competition. The company reported earnings of $13.4 billion in full year 2016, about $13.8 billion less than five years earlier.

A director battle at Procter & Gamble is a massive undertaking because of the company's $231 billion market capitalization. It would be the largest director-election proxy fight in the U.S., far outstripping Peltz's 2015 battle at DuPont Co. (DD - Get Report)