Social media companies such as Twitter, Google and Facebook are insisting to Sen. Mike Lee that they are not biased toward conservatives, but he’s not buying it.

He made that clear Thursday after looking at their responses to a series of questions he sent them about how and why they moderate or cut comments online — after he had attacked what he says is their warping of public debate by unfairly silencing many conservatives.

“The responses received from the tech companies about bias against conservatives at their firms were completely unpersuasive,” Lee said in a statement Thursday.

“I continue to be concerned about the ideological discrimination going on at these firms and I believe further oversight will be necessary in order to obtain the facts and answers that the American people deserve.”

Earlier this summer, Lee dangled the possibility of breaking up what he says are monopolies by the companies for what he says is their “heavy-handed censorship” of conservatives including President Donald Trump.

Such threats have extra weight because Lee is chairman of the Senate Judiciary Antitrust Subcommittee, which oversees legislation about monopolies. He has scheduled a hearing on Tuesday on whether Google and other tech giants are “stacking the deck” in online advertising.

Lee complained in earlier letters, “In recent years, conservative voices like The Federalist, PragerU, President Trump, Senator Marsha Blackburn, Senate Majority Leader Mitch McConnell, Donald Trump Jr., churches, religious schools, Christian groups and others have found themselves deplatformed, demonetized or otherwise penalized for expressing their opinions.”

For example, he complained social media companies removed a video — which President Trump had retweeted — published by the right-wing Breitbart News that featured a group of people wearing white lab coats calling themselves “America’s Frontline Doctors” who made dubious claims, including that masks are not needed to fight COVID-19 and that studies saying hydroxychloroquine is ineffective are “fake science.”

So Lee wanted to know such things as what moderation standards the tech giants employ, and how they screen employees they hire to do that moderation.

Among some responses released on Thursday were:

• Twitter wrote that it “does not use political viewpoints, perspectives, ideology or party affiliation to make any decisions, whether related to automatically ranking content or how we enforce our rules.”

It also said, “Individuals are not permitted to propagate false or misleading information around COVID-19 diagnostic criteria or procedures.”

Additionally, “Twitter does not use political ideology as a factor when hiring content moderators. Twitter moderators are provided ongoing training on how to enforce our rules impartially.”

• Google wrote, “Our content moderation standards are apolitical, unbiased and do not preference one point of view over another. We apply our policies to all content creators across the board and will not allow any form of political bias.”

On COVID-19, it says it evaluates authoritative information and then “removes harmful misinformation." It added that "we’ve removed 200,000 coronavirus videos globally with dangerous or misleading coronavirus information on YouTube.”

It added that on its YouTube product, “We’re committed to maintaining an open platform where many different viewpoints and types of speech are welcome, including speech that some people might find problematic. We consult with experts as we look to draw the line in the right place.”

• Facebook said it asked former GOP Sen. Jon Kyl to conduct a review of potential anticonservaitve advertising on Facebook, and he worked with 130 conservative politician and groups on then.

The company said it led to changes including: providing more information about why specific posts are on its news feed; launching an appeals process for enforcement actions; creating a new and diverse oversight board for content; and making changes in labeling for political and social issue ads.

“We take the safety of our community seriously and work hard to prevent abuse on our platform — and we’re committed to being transparent about how we do this,” it said.

• Squarespace responded to Lee’s complaint about the removal of the “America’s Frontline Doctors” website and video from its platform.

It said after receiving numerous complaints, “We found that the video claimed that there was a cure for COVID-19.The FDA has said that such content could lead to serious and life-threatening harm.”

It added that such statements about a cure had been made as if they were facts, not political opinion, so they were removed.