Facebook chief Mark Zuckerberg admitted on Monday to errors in privacy and security lapses as he was grilled by lawmakers at the US Congress. In prepared remarks released by a congressional panel, Zuckerberg admitted he was too idealistic and failed to grasp how the platform -- used by two billion people -- could be abused and manipulated. "We didnt take a broad enough view of our responsibility, and that was a big mistake. It was my mistake, and Im sorry," Zuckerberg said in his written testimony released by the House commerce committee. "I started Facebook, I run it, and Im responsible for what happens here." In his written remarks, Zuckerberg called Facebook "an idealistic and optimistic company" and said: "We focused on all the good that connecting people can bring." But he acknowledged that "its clear now that we didnt do enough to prevent these tools from being used for harm as well. That goes for fake news, foreign interference in elections, and hate speech, as well as developers and data privacy." He made the rounds on Capitol Hill with his assistant Andrea Besmehn for private meetings with lawmakers ahead of hearings at the Senate on Tuesday -- a key test for the Facebook founder. The 33-year-old is to testify before senators and House lawmakers on Wednesday amid a firestorm over the hijacking of data on millions of Facebook users by the British firm Cambridge Analytica, which worked with Donald Trumps campaign. Zuckerberg said he has called for more investments in security that will "significantly impact our profitability going forward," adding: "I want to be clear about what our priority is: protecting our community is more important than maximizing our profit." He recounted a list of steps announced by Facebook aimed at averting a repeat of the improper use of data by third parties like Cambridge Analytica, and noted that other applications were also being investigated to determine if they did anything wrong. "Were in the process of investigating every app that had access to a large amount of information before we locked down our platform in 2014," said Zuckerberg. "If we detect suspicious activity, well do a full forensic audit. And if we find that someone is improperly using data, well ban them and tell everyone affected." After meeting with Zuckerberg on Monday, Senator Bill Nelson told reporters that Zuckerberg appears to be taking the matter seriously. "I believe he understands that regulation could be right around the corner," Nelson said. Nelson said lawmakers would be looking at other social media sites in determining any new regulations. Facebook "happens to be the point of the spear, but all these other app sites that get your personal data, thats another way of us losing our privacy," Nelson said. On Tuesday, Zuckerberg is scheduled to testify before a joint hearing of the Senate Commerce and Judiciary Committees, amid calls to regulate internet-based companies The prospect of new laws that restrict Facebook and other internet companies is extremely unlikely not only because of a lack of political will and the effective lobbying of technology companies but because few lawmakers want to grapple with the sheer complexity of the technical issues involved. Senator Dianne Feinstein, the top Democrat on the Judiciary Committee, told reporters after speaking with 33-year-old Zuckerberg, that he “was a very nice young man” who “obviously knows what he’s doing and has a very pleasant personality.” White House Press Secretary Sarah Sanders declined to say on Monday if new regulations were needed. “I don’t have a specific policy announcement on that front, but I think we’re all looking forward to that testimony.” Republicans are generally against more corporate regulation and they are not persuaded that tech companies need more of it. “I don’t want to hurt Facebook. I don’t want to regulate them half to death,” said Republican Senator John Kennedy of Louisiana, a member of the Judiciary Committee “But we have a problem. Our promised digital utopia has minefields in it.” Facebook has taken a series of proactive steps to make up for massive lapses in protecting user data, as lawmakers signaled they intend to get tough on privacy. Last week, the company announced new privacy tools to be in place in user news feeds on Monday, and said it would notify the 87 million users affected by the data hijacking scandal, amid probes underway on both sides of the Atlantic. Over the weekend, it said it had suspended another data analysis firm, US-based Cubeyou, after reports that it had used private data harvested from psychological testing apps for commercial purposes. It also suspended the Canadian firm AggregateIQ over apparent collaboration with Cambridge Analytica. On Friday, Facebook sought to quell some concerns over political manipulation of its platform by announcing support for the "Honest Ads Act" that requires election ad buyers to be identified, and to go further with verification of sponsors of ads on key public policy issues. Zuckerberg said the change will mean "we will hire thousands of more people" to get the new system in place ahead of US midterm elections in November. "Were starting this in the US and expanding to the rest of the world in the coming months," Zuckerberg said. On Monday, Facebook agreed to supply proprietary data for a study on its role in elections and democracy. "The focus will be entirely forward looking. And our goals are to understand Facebooks impact on upcoming elections -- like Brazil, India, Mexico and the US midterms -- and to inform our future product and policy decisions," Facebook said in a statement. Facebook has said it has seen little impact on its business from the privacy scandal despite a #deleteFacebook movement and concerns from advertisers. But Brian Wieser of Pivotal Research said the entire digital advertising industry, of which Google and Facebook are the leaders, could be impacted by the scandal. The changes announced by Facebook and Google restricting third-party access "indicate a higher likelihood that both companies will raise their walls ... Both of these trends will likely harm ad tech companies focused on buying media or otherwise focused on the Facebook and Google ecosystems."