Apple's powerful role as gatekeeper of the App Store has long frustrated the makers of apps who must abide by its rules or risk losing access to hundreds of millions of customers who own Apple devices.
Now one of Apple's biggest rivals, the music streaming service Spotify, says Apple is abusing its position and violating European antitrust laws.
In an aggressive attempt to undercut Apple's power, Spotify said on Wednesday that it had filed a complaint with European regulators, accusing Apple of using its App Store to squash companies that compete with its services, including Apple Music.
Spotify's complaint comes at a perilous moment for the world's biggest tech companies. Scrutiny over Silicon Valley's power has been increasing in recent years, and it has already become a topic among Democratic presidential hopefuls.
One of them, Sen. Elizabeth Warren of Massachusetts, last week proposed breaking up the tech giants as a remedy to their unfair advantages. One of her ideas was to separate the App Store from Apple.
"Spotify's complaint is just the latest example of what can happen when these enormous companies abuse their power to undermine competition," Warren said in a statement Wednesday. "We need a level playing field, and that starts by breaking up giant tech companies who both own a marketplace and operate in that same marketplace."
Apple's role as a make-or-break arbiter has long frustrated app makers by imposing rules and charging a fee of up to 30 percent on anything sold through its App Store.
Spotify, which has headquarters in Luxembourg and Sweden, said it had told the European Commission, an aggressive regulator of the tech industry, that the policies were not just a costly nuisance but a "tax" that violated competition laws and merited an investigation.
The policies have been particularly vexing for companies, like Spotify, that compete with Apple. Spotify and Apple Music are the world's largest music streaming services.
"They continue to give themselves an unfair advantage at every turn," Daniel Ek, Spotify's chief executive, said in a message posted on the company's website. He said Apple was acting as both "player and referee to deliberately disadvantage other app developers."