Investment management firm Red Mountain Capital Partners LLC said in a letter on Monday that it is pushing apparel and accessories maker Deckers Outdoor Corp's board to explore a sale of the company.

Red Mountain, which owns about 3.3 percent of Deckers' outstanding shares, said in the letter that the apparel maker's stock had underperformed across all major indices over the past three to five years.

"This underperformance has been driven largely by management's consistently poor capital allocation decisions," Red Mountain's Managing Partner Willem Mesdag said.

The letter comes nearly two months after activist hedge fund Marcato Capital Management LP reported a 6 percent stake in Deckers, saying it intends to discuss strategy and options for the struggling maker of UGG boots and apparel.

Red Mountain also said the value of a sale to a strategic or financial buyer is substantially higher than the operating plan announced by the Deckers' management on Feb 2.

"We appreciate the views of all of our stockholders and we value constructive input toward the shared goal of enhancing stockholder value," a Deckers representative told Reuters in response to the letter.

Sales of Deckers' sheepskin UGG boots, popular across U.S. cities, college campuses and malls, exploded to $1.52 billion in fiscal 2016 from $37 million in 2003. However, growth has slowed.

Deckers shares were up about 3 percent at $58.01 in extended trading on Monday.