Andrew Hoyle/CNET

Beleaguered HTC's woes just keep piling up. Following dwindling market share and a plummeting stock price, on Sunday it was announced that the smartphone maker is to be removed from the Taiwan Stock Exchange's FTSE TWSE Taiwan 50 Index.

The index is a list of 50 highly valued Taiwanese blue chip stocks, with the companies that populate it comprising nearly 70 percent of the country's stock market. HTC will be replaced on 21 September by elastic fabric maker Eclat Textile. HTC did not immediately respond to a request for comment.

The first mobile phone manufacturer to take advantage of Google's Android software, HTC was once a strong player in the market, but in the past several years has steadily lost ground to competitors Samsung, Apple and, more recently, efficient Chinese manufacturers such as Xiaomi and Huawei.

Yahoo Finance, screenshot by Daniel Van Boom/CNET

The removal of the smartphone pioneer from the Taiwan 50 follows the August announcement that it would lay off 15 percent of its workforce and slash operating costs by 35 percent, as it reported its lowest monthly revenue in eight years.

HTC's current global smartphone market share has been estimated to be around 2 percent -- around one fifth of the 10.7 percent share it had back in 2011. By comparison, Samsung holds 21.4 percent of the market, according to analyst IDC.

The company's 2015 flagship phone, the One M9, was widely considered a strong offering on its own merits upon its release in April. But it looked and felt too similar to last year's M8, leading to disappointing sales.

HTC CEO Cher Wang told the Wall Street Journal in March that the company will be "refocusing on our product advantage...and moving beyond the smartphone business."

That was a reference to HTC's foray into virtual reality with the Vive headset. Built in collaboration with video game developer Valve, the headset has garnered plenty of positive attention ahead of its intended 2016 release. But with competition from Sony and Facebook-owned Oculus in this nascent product category, it seems unlikely to be a short-term hit.