Sen. Mark Warner, D-Va., told CNBC on Wednesday that federal regulators should carefully look at Google's proposed $2 billion purchase of FitBit, which comes with a treasure trove of consumer health and wellness data.

"The Fitbit deal needs a high, high level of scrutiny, if we're going to have Google take on again all this personal data," said the former Virginia governor, now a leading voice in the Senate on tougher tech regulations.

In announcing the deal last month, both companies stressed that Fitbit data won't be used for Google ads. They also said that Fitbit users will have the choice to review, move or delete their data.

However, Warner expressed skepticism, saying in a "Squawk Box" interview that "large platform companies have not had a very good record of protecting the data or being transparent with consumers."

"I can't totally blame them," he added. "If Congress doesn't set rules of the road, asking them to self-regulate is, frankly, just not a viable option."

The senator also sounded a note of caution about Google's plans to get into banking. A source familiar with the situation, confirming a Wall Street Journal report, said Wednesday the company plans to offer checking accounts next year.

Earlier this week, the Journal first disclosed a Google partnership with major hospital network Ascension to collaborate on tools to help make sense of information about patients and help doctors search medical records.

These efforts by Alphabet's Google, which will give it access to more and more consumer data, fuel the debate on whether big tech companies are acting as good stewards of users' private information.

Warner, a successful tech entrepreneur before he got into politics, told CNBC, "I'm a tech guy. I'm all for innovation," stressing he's not saying these types of deals should necessarily be blocked.

However, he said he's concerned about "giant tech platforms entering into new fields before there are some regulatory rules of the road."

"Because once they get in, the ability to extract them out is going to be virtually impossible," he said.

Google declined to comment on Warner's comments. FitBit also did not comment, referring CNBC to a press release that announced the acquisition.

- CNBC's Kevin Stankiewicz contributed to this report.