Testimony in Congress this week by the whistleblower Frances Haugen should prompt action to implement meaningful oversight of Facebook and other tech giants, the influential California Democrat Adam Schiff told the Guardian in an interview to be published on Sunday.

“I think we need regulation to protect people’s private data,” the chair of the House intelligence committee said.

“I think we need to narrow the scope of the safe harbour these companies enjoy if they don’t moderate their contents and continue to amplify anger and hate. I think we need to insist on a vehicle for more transparency so we understand the data better.”

Haugen, 37, was the source for recent Wall Street Journal reporting on misinformation spread by Facebook and Instagram, the photo-sharing platform which Facebook owns. She left Facebook in May this year, but her revelations have left the tech giant facing its toughest questions since the Cambridge Analytica user privacy scandal.

At a Senate hearing on Tuesday, Haugen shared internal Facebook reports and argued that the social media giant puts “astronomical profits before people”, harming children and destabilising democracy via the sharing of inaccurate and divisive content.

Haugen likened the appeal of Instagram to tobacco, telling senators: “It’s just like cigarettes … teenagers don’t have good self-regulation.”

Richard Blumenthal, a Democrat from Connecticut, said Haugen’s testimony might represent a “big tobacco” moment for the social media companies, a reference to oversight imposed despite testimony in Congress that their product was not harmful from executives whose companies knew that it was.

The founder and head of Facebook, Mark Zuckerberg, has resisted proposals to overhaul the US internet regulatory framework, which is widely considered to be woefully out of date.

He responded to Haugen’s testimony by saying the “idea that we prioritise profit over safety and wellbeing” was “just not true”.

“The argument that we deliberately push content that makes people angry for profit is deeply illogical,” he said. “We make money from ads, and advertisers consistently tell us they don’t want their ads next to harmful or angry content.”

Schiff was speaking to mark publication of a well-received new memoir, Midnight in Washington: How We Almost Lost Our Democracy and Still Could.

The Democrat played prominent roles in the Russia investigation and Donald Trump’s first impeachment. He now sits on the select committee investigating the deadly attack on the US Capitol on 6 January, by Trump supporters seeking to overturn his election defeat – an effort in part fueled by misinformation on social media.

In his book, Schiff writes about asking representatives of Facebook and two other tech giants, Twitter and YouTube, if their “algorithms were having the effect of balkanising the public and deepening the divisions in our society”.

Facebook’s general counsel in the 2017 hearing, Schiff writes, said: “The data on this is actually quite mixed.”

“It didn’t seem very mixed to me,” Schiff says.

Asked if he thought Haugen’s testimony would create enough pressure for Congress to pass new laws regulating social media companies, Schiff told the Guardian: “The answer is yes.”

However, as an experienced member of a bitterly divided and legislatively sclerotic Congress, he also cautioned against too much optimism among reform proponents.

“If you bet against Congress,” Schiff said, “you win 90% of the time.”