US President Donald Trump on Tuesday renewed his attack on Twitter, accusing the social network of tampering with his followers out of bias favoring the Democrats.

Twitter has purged suspicious accounts, resulting in declines in followers for some prominent users, but there is no evidence that Trump has been targeted for political reasons.

The president has actually seen a healthy increase in followers since the start of October.

US President Donald Trump has renewed his attack accusing America's tech giants of a liberal bias, saying that Twitter is tampering with his followers.

"Facebook, Twitter and Google are so biased toward the Dems it is ridiculous!" Trump said in a tweet. "Twitter, in fact, has made it much more difficult for people to join @realDonaldTrump. They have removed many names & greatly slowed the level and speed of increase. They have acknowledged-done NOTHING!"

It is not the first time Trump has raised concerns about his Twitter followers. In late October, the president said Twitter had "removed many people from my account" and made it harder to follow him.

"They have stifled growth to a point where it is obvious to all," he wrote. "A few weeks ago it was a Rocket Ship, now it is a Blimp! Total Bias?"

Read more: This graph shows 90% of political donations from Google workers went to the Democrats

Twitter said at the time that any decline in growth could be linked to its purge of suspicious accounts that spread misinformation. "Many prominent accounts have seen follower counts drop, but the result is higher confidence that the followers they have are real, engaged people," a spokesman told Reuters.

A Twitter spokesman repeated this statement when contacted by Business Insider. "Our focus is on the health of the service, and that includes work to remove fake accounts to prevent malicious behavior," he said.

Trump's Twitter following has actually increased healthily since the start of October. Internet archives show he had 54.8 million followers on October 1, compared with 56.3 million on Tuesday — a rise of 1.5 million followers.

This rate of growth in followers for Trump was down roughly 17% from that of the previous quarter, though the more recent data did not include three full months. From July through September, his following increased by 1.7 million, to 54.8 million followers from 53.1 million.

Trump has repeatedly accused Facebook, Google, and Twitter of favoring Democrats in their services. He has not provided evidence that supports his claims, however, and experts say there is little to support his accusations.

Ari Ezra Waldman, the director of the Innovation Center for Law and Technology at the New York Law School, told Business Insider this month that there was "zero" evidence to support the theory that Google was fixing search results against Republicans. GOP lawmakers grilled Google CEO Sundar Pichai earlier this month about what they framed as search bias against conservative voices.

"What comes up on search results on Google, for example, is the product of Google's highly complex and proprietary algorithm, which is sensitive to what other people click on, share, and so forth," Waldman said.

"So, if critical articles about Donald Trump are coming up first, that just means that critical articles about Donald Trump are being shared more, clicked on more, and searched for more."