Donald Trump’s return to Facebook and Instagram will “fan the flames of hatred and division”, a Democratic congresswoman said, amid liberal outrage after parent company Meta announced its decision to lift a ban on the former US president imposed after the January 6 Capitol attack.

Jan Schakowsky, of Illinois, said: “Reinstating former president Trump’s Facebook and Instagram accounts will only fan the flames of hatred and division that led to an insurrection.”

Trump was impeached for inciting the January 6 riot, a deadly attempt to overturn his defeat by Joe Biden in the 2020 election.

Trump was also banned from major social media platforms. His ban from Twitter was lifted in November, after the site was purchased by the Tesla owner, Elon Musk. Trump has not tweeted since, although he is active on his own social media platform and would-be Twitter rival Truth Social.

Announcing Meta’s decision, its president of global affairs, the former British deputy prime minister Nick Clegg, told NBC “the rough and tumble of democratic debate should play out on Facebook and Instagram as much as anywhere else”.

Schakowsky countered: “The reinstatement of Trump’s accounts show that there is no low [Meta chief executive] Mark Zuckerberg will not stoop to in order to reverse Meta’s cratering revenue and stagnant consumer growth, even if it means destroying our democracy.”

Among other Democrats, Adam Schiff, a former House intelligence committee chair, said Trump had “shown no remorse [or] contrition” for January 6, and Facebook had “caved, giving him a platform to do more harm”.

Eric Swalwell, like Schiff now barred from the intelligence committee by Republican leaders, said: “We know that [Trump’s] words have power and they inspire, and then the leaders in the Republican party, like Speaker [Kevin] McCarthy, they don’t condemn them. And so when they’re not condemned, they’re a green light and open lane for more violence to occur.”

Some liberal groups also scorned the decision.

Angelo Carusone, president of Media Matters for America, said: “Meta is refuelling Trump’s misinformation and extremism engine … one that will put us on a path to increased violence.”

Noah Bookbinder, president of Citizens for Responsibility and Ethics in Washington, or Crew, pointed out that Meta was not bound by constitutional free speech protections.

“Facebook is not the government,” he wrote. “The first amendment does not require it to give Donald Trump a platform for speech. And the first amendment does not protect speech to incite an insurrection or overturn an election. The justifications for this are nonsense.”

But there was support for Meta among civil liberties groups.

Anthony Romero, executive director of the American Civil Liberties Union, said: “Like it or not, President Trump is one of the country’s leading political figures and the public has a strong interest in hearing his speech.

“The biggest social media companies are central actors when it comes to our collective ability to speak – and hear the speech of others – online. They should err on the side of allowing a wide range of political speech, even when it offends.”

Trump used his own platform, Truth Social, to celebrate.

He wrote: “Facebook, which has lost billions of dollars in value since ‘deplatforming’ your favorite president, me, has just announced that they are reinstating my account. Such a thing should never again happen to a sitting president, or anybody else who is not deserving of retribution!”

CNN reported that Meta said Trump would be “permitted to attack the results of the 2020 election without facing consequences” but would face action if he “were to cast doubt on an upcoming election – like, the 2024 presidential race”.

Crew, the ethics watchdog, was not alone in expressing skepticism. It said: “If anyone thinks Donald Trump will rejoin Facebook, then not do the same exact thing he did before, well, they clearly don’t know anything about Donald Trump.”