The US Department of Justice has opened an investigation into whether companies such as Amazon, Facebook and Google have “stifled innovation” by thwarting competition unlawfully.

The department's antitrust division did not name the companies but announced on Tuesday that it was reviewing market-leading “online platforms” to see how they have come to power and whether they engaged in illegal practices that reduced competition and made it difficult for smaller companies to thrive.

The investigation raises the prospect that the companies could be fined, forced to change their business models, or in an extreme scenario, broken up.

The Justice Department said it had received a number of complaints against big tech companies that include allegations surrounding search, social media and retail services.

The investigation signals increasing anti-technology rhetoric in Washington, which had long been considered an ally of Silicon Valley. President Donald Trump has repeatedly accused technology companies of bias against conservatives, and presidential hopeful Elizabeth Warren has pushed for breaking up large tech companies, which critics have avoided the scrutiny of the law for too long. There have been concerns over Facebook, which operates WhatsApp and Instagram, and Google-owner Alphabet, which owns numerous different companies across different industries.