Spotify (SPOT) is escalating its public battle with Apple (AAPL) over its controversial app store practices.

In a lengthy thread posted to Twitter on Wednesday, Spotify CEO Daniel Ek wrote: "As countless entrepreneurs have highlighted, Apple is shameless in their bullying including our recent efforts to help authors sell more audiobooks."

"Apple acts in self interest but also doesn’t seem to care about the law or courts," Ek continued, adding: "How much longer will we look away from this threat to the future of the internet? How many more consumers will be denied choice? There’s been a lot of talk. Talk is helpful but we need action."

Ek's latest comments come as prominent voices in the tech world are again speaking out against Apple's App Store practices following Elon Musk's recent comments.

Musk, CEO of Tesla and Twitter, tweeted Apple's practices were “concerning” and recentlyaccused Apple of suppressing speech by requiring apps in its store to abide by certain content standards.

In one tweet, Musk specifically tagged Apple CEO Tim Cook’s Twitter account.

'Apple continues to stand in the way'

The music streaming platform, which launched its audiobook business in September, has consistently called out Apple's "anti-competitive behavior."

In a blog post published in October, Spotify wrote: "Apple continues to stand in the way of Spotify’s and other developers’ abilities to provide a seamless user experience, and its restrictions hurt both creators and consumers alike."