It followed news that the company lost 200,000 subscribers in the first three months of the year. Netflix has pledged to introduce a cheaper ad-funded subscription tier and crackdown on account sharing in a bid to restart growth.
Ackerman, worth an estimated $3.2 billion, wrote in a letter to Perishing Square investors this week: “While we believe these business model changes are sensible, it is extremely difficult to predict their impact on the company’s long-term subscriber growth, future revenues, operating margins, and capital intensity.
“While Netflix’s business is fundamentally simple to understand, in light of recent events, we have lost confidence in our ability to predict the company’s future prospects with a sufficient degree of certainty.”
Ackman’s investment firm Pershing Square only backed the streaming giant in January, buying 3.1 million shares at the cost of $1.1 billion (£842 million).
At the time, Ackman told investors he was “all-in on streaming”, adding the Netflix stake to one in Universal Music Group.
Netflix saw $47 billion (£36 billion) wiped off its value in the opening minutes of trading in New York on Wednesday as it warned that it could lose another 2.5 million subscribers this year. Its quarterly fall in subscriber numbers was the first fall in a decade.
The streaming service has now seen its market value decline by $160 billion (£122 billion) since the start of the year. Its decision in early March to suspend service in Russia after the country’s invasion of Ukraine resulted in the loss of 700,000 members alone.