Billionaire investor Daniel Loeb has stepped up pressure on food group Nestle in a letter that urged its board to be "sharper," "bolder" and "faster" in spinning off businesses and untangling its complex management structure. 

"This is a call for urgency - rather than incrementalism," said Loeb's letter. 

It came with a 34-page presentation with recommendations and critiques. 

Third Point, the $18 billion hedge fund which has invested more than $3 billion in Nestle, has also launched a website to push its case. 

Loeb's letter, seen by Reuters, demanded that Nestle spin off more businesses that do not fit its strategy including ice cream, frozen foods, and confectionary.

He also wants Nestle to divide itself internally into three divisions - beverages, nutrition and grocery - and add an outsider to the board with expertise in the food and beverage business. 

Each division should have its own CEO, regional structure and marketing heads, Loeb said. 

This would "simplify (Nestle's) overly complex organisational structure," the letter said.

Loeb's demands came roughly on the first anniversary of his investment in Nestle and at a time of significant merger activity in the food industry. 

For months, the activist investor who previously pushed for change at Yahoo and Dow Chemical as well as other companies watched and periodically made supportive public comments about Nestle's new chief executive officer, Mark Schneider.

But his letter made clear that Third Point is no longer willing to keep its critiques behind closed doors.

It criticised Nestle's slow sales growth, declining stock price and its failure to sell off more pieces that do not fit its "nutrition health and wellness" strategy. 

The fund manager's biggest concern was corporate strucure, with the board of directors in charge of strategic direction. 

"Nestle’s insular, complacent, and bureaucratic organisation is overly complex, lethargic, and misses too many trends," Loeb said in the letter. 

In early 2017, the Swiss company hired Schneider, a German, as its first non-Swiss CEO in nearly a century. He had won praise for overhauling Fresenius Medical Care. 

But former CEO Paul Bulcke remained Nestle's board chair, which raised eyebrows among governance experts. Insiders say that after months at the helm, Schneider has yet to bring in a broad team of his own. 

Industry experts say CEOs sometimes privately welcome public critiques from big shareholders, as effective cover to push through changes more aggressively. 

Loeb has only put together websites twice before - at Yahoo and Dow Chemical, but he has been vocal at plenty of companies and most recently pushed for United Technologies to break itself into three companies.