Last month, Senator Mark Warner left a closed-door briefing with Twitter visibly frustrated. He said he doubted whether the tech titan grasped the gravity of the investigation into Russian election meddling, and fumed to reporters that the company’s presentation to congressional investigators about how Russia used its platform to influence the 2016 race was “frankly, inadequate on every level”.

The public scolding was yet another sign of Washington’s growing impatience at Silicon Valley, with the Virginia senator emerging as one of the loudest critics in Congress. This month he co-authored new legislation that would require internet companies to disclose who purchased online political ads on their platforms, the most aggressive attempt yet to regulate big tech.

“Part of the reason these guys have gotten away with no regulation for 20 years is because they convinced Washington that the industry is too complicated,” said Jonathan Taplin, author of Move Fast and Break Things: How Facebook, Google, and Amazon Cornered Culture and Undermined Democracy.

“But it is very hard to say that to Mark Warner. He’s been in the technology business. He’s been an investor. He can’t be smoked.”

As the political sands shift for technology companies, and executives from Facebook, Google and Twitter are set to testify before congressional panels on Capitol Hill this week, there are perhaps few US senators who understand the industry as deeply as Warner, a former entrepreneur and executive who amassed a fortune investing in technology and telecommunications.

Friends and former colleagues insist the Democratic senator is as pro-business and pro-growth as he ever was, still closer on the ideological spectrum to Republican moderate Susan Collins than leftwing firebrand Bernie Sanders. He maintains a coterie of friends and confidants in Virginia’s tech world whom he regularly communicates with and is on friendly terms with a number of Silicon Valley executives.

But, as vice-chair of the Senate intelligence committee investigating Russian interference in the US election and studying how to prevent it from happening again in the 2018 congressional midterms, Warner has developed a more aggressive posture toward big tech.

“Mark does not suffer fools gladly,” said Bobbie Kilberg, the president and CEO of the Northern Virginia Technology Council. “By this I mean that when you meet with him, you better know what you’re talking about.”

However, she said, “when he is in a role of scrutinizing it he comes from it with a level of sophistication and respect. They know he will be fair.”

Warner was the co-founder of a company that became Nextel, the wireless service operator that merged with Sprint Corp in 2005 in a $35bn deal.

Warner has said publicly and privately that the investigation is “probably the most important thing I’ve done” and his friends say it has renewed his zeal for the institution he serves.

“I think it goes without saying his first few years were frustrating,” said Saxby Chambliss, a retired Republican senator from Georgia.

Before arriving in the Senate in 2008, Warner was the popular governor of Virginia, leaving office in 2006 with high public approval ratings. He enjoyed the executive role and championed bipartisanship during his tenure, even convincing a Republican legislature to reform the tax code. But when he reached the Senate, Warner felt stonewalled by the slow pace of progress and entrenched partisanship.

“When he made a decision as governor something happened. He quickly found that he didn’t have the same opportunity in the Senate,” Chambliss said. “He’s very appreciative of the fact that he’s the vice-chair of the [Senate] intelligence committee.”

On Wednesday, a day after appearing before the Senate crime subcommittee, executives from Google, Facebook and Twitter will go before Warner’s committee, where lawmakers say the tone of the meeting will depend on how forthcoming the companies are prepared to be about how Russia used their platforms to spread misinformation and sow discord during the election.

“If they see this as a public relations problem that they can paper over then you’ll see some frustration from the Senate,” said Angus King, an independent senator from Maine and a member of the committee.

“This was an attack on this country. I would think that they as well as we would want to understand how that happened.”

Ahead of the hearings, Facebook and Twitter have introduced internal efforts to increase transparency around the way the accept and display political advertisements. And earlier this month, Facebook dispatched Sheryl Sandberg, its chief operating officer, to Washington as the company faced intensifying criticism from lawmakers and the public.

“Talk is cheap,” Warner said, after the Twitter briefing. “What I’d like to see is a real effort to try to work with us in a way that we can make sure Americans understand the nature and the extent of the threat.”

Earlier this month, Warner and co-author Amy Klobuchar, a Democrat of Minnesota, unveiled legislation that would force Google, Facebook and other digital platforms to disclose who purchased online political advertisement.

But opposition is already whirring to life. During a House hearing last week, Randall Rothenberg, the president of Interactive Advertising Bureau, which represents Facebook, Google, Twitter and other big content and advertising companies, argued in favor of “self-regulation”, which he claimed would “actually go further than this Congress can go in enforcing the rules”.

Taplin, who is also the director USC Annenberg Innovation Lab, said Warner is “calling bluff” on the big tech companies by introducing the disclosure legislation.

“They did a lot of PR spin up front,” he said. “Now Warner is saying to them, OK if you’ve already said your willing to do this, then let’s put it into law.”