The chief executive officer of Alphabet Inc's Google on Monday defended the integrity of the company's products a day ahead of a congressional hearing where he is expected to face tough questions from U.S. lawmakers. The technology company has been under fire on Capitol Hill over issues including why it delayed disclosing vulnerabilities with its Google+ social network, whether it will restart its search engine in China and if it is biased against Republicans. Three Democratic senators wrote the Federal Trade Commission in October asking the agency to investigate Google+. In written testimony to the House Judiciary Committee made public on Monday, CEO Sundar Pichai said he led the company "without political bias." "We work hard to ensure the integrity of our products, and we\u2019ve put a number of checks and balances in place to ensure they continue to live up to our standards," Pichai's testimony said. "I lead this company without political bias and work to ensure that our products continue to operate that way. To do otherwise would go against our core principles and our business interests." Read Also| USCIRF hearing on religious freedom in India postponed Pichai agreed in September to testify over Republican concerns that the company is biased against conservatives. Google has repeatedly denied this. The company faced renewed criticism on Capitol Hill after senior executives skipped a high-profile Senate Intelligence Committee hearing earlier in September. Google previously told U.S. lawmakers it was considering "a variety of options" to offer additional services in China, but declined to detail plans for addressing Chinese censorship. The company has been criticized after reports it was considering re-entering China\u2019s search engine market and would comply with its internet censorship and surveillance policies.