WASHINGTON (Reuters) - U.S. lawmakers, alarmed that foreign entities used the internet to influence last year's election, introduced legislation on Thursday to extend rules governing political advertising on television, print and radio to also cover social media like Facebook Inc FB.O.

FILE PHOTO: Facebook logo is seen at a start-up companies gathering at Paris' Station F in Paris, France on January 17, 2017. REUTERS/Philippe Wojazer/File Photo

Democratic Senators Amy Klobuchar and Mark Warner and Republican John McCain introduced the “Honest Ads Act,” one of the strongest efforts in Congress yet to address allegations of Russian meddling in the 2016 presidential campaign.

The legislation would expand existing election law covering television and radio outlets to apply to paid internet and digital advertisements on platforms like Facebook, Twitter Inc TWTR.N and Alphabet Inc's GOOGL.O Google.

“Our laws have failed to keep up with evolving technology and the capabilities of our foreign adversaries,” Klobuchar told a news conference.

The measure would also require digital platforms with at least 50 million monthly views to maintain a public file of all electioneering communications purchased by anyone spending more than $500.

And it would require online platforms to make “all reasonable efforts” to ensure that foreign individuals and entities are not buying political advertisements to influence the U.S. electorate.

Companion legislation was introduced in the House of Representatives by Republican Representative Mike Coffman and Democrat Derek Kilmer.

Social media companies have become an increasing focus of congressional investigations into allegations that Russia sought to meddle in the 2016 U.S. election on behalf of Republican candidate Donald Trump, something now-President Trump and Moscow deny.

Warner, who was a technology executive before entering politics, said $150,000 of ads paid for in rubles may be only the “tip of the iceberg” in terms of how many political advertisements were bought by foreign firms. He said advertisements could have been purchased using dollars, euros or pounds.

U.S. law bars foreigners from spending money to attempt to influence American elections.

Warner and Klobuchar acknowledged that the companies have resisted the legislation. But Warner said, “It’s our hope that the social media companies and platform companies will work with us.”

WILL IT PASS?

It was not immediately clear how much support the act would receive in Congress or when it might come up for a vote.

Social media companies have begun a lobbying campaign to at least influence, if not prevent, the bill.

The companies said they are open to working with Congress and have been turning over information, but are legally obligated to protect their users’ privacy. Facebook has turned over thousands of ads to congressional investigators and its chief operating officer, Sheryl Sandberg, met with members of Congress last week.

Google said it was look at steps it could take on its various platforms and would work closely with Congress, the Federal Election Commission and the industry to come up with solutions.

“We support efforts to improve transparency, enhance disclosures and reduce foreign abuse,” Google spokeswoman Riva Sciuto said in an emailed statement.

Klobuchar and Warner said it was possible the measure could be offered an amendment to another larger piece of legislation.

Warner is vice chairman of the Senate Intelligence Committee, one of the congressional panels investigating the alleged Russian hacking and the possibility that Trump’s campaign colluded with Moscow.

Klobuchar is the ranking Democrat on the Senate Rules Committee, which helps oversee elections. And McCain is chairman of the Senate Armed Services Committee.

They said they would like it to become law by early next year, well ahead of the November 2018 U.S. mid-term elections, in which every seat in the 435-member House and about one third of the 100-seat Senate will be up for grabs

Many lawmakers and other U.S. officials have said they fear Russian efforts to meddle in those polls as well.

Separately, Facebook, Twitter and Google said Thursday they would send their general counsels to testify Nov. 1 before public hearings of the Senate and House Intelligence Committees.

General counsel Colin Stretch will be the Facebook representative to testify before both committees, company spokesman Andy Stone said. The company’s high-profile Chief Executive Officer Mark Zuckerberg and COO Sandberg will not appear.

A Twitter spokeswoman said Acting General Counsel Sean Edgett will represent the microblogging site. A Google spokeswoman said General Counsel Kent Walker would represent that company.