By Andy Sullivan
WASHINGTON (Reuters) - The U.S. Department of Justice's internal watchdog told Congress on Wednesday that the FBI made "basic and fundamental errors" during a politically sensitive investigation into Donald Trump's presidential campaign in 2016.
In testimony that did not deviate from a report issued on Monday, Inspector General Michael Horowitz also said he had found the FBI had sufficient cause to open an investigation of any possible Trump campaign ties to Russia and he had not found evidence that it was motivated by political bias.
Trump and fellow Republicans have accused the agency of bias and Horowitz's review provided grist for both Republicans and Democrats in the debate over the legitimacy of an investigation that clouded the first 2 -1/2 years of Trump's presidency.
Senate Judiciary Committee chairman Senator Lindsey Graham told a hearing that the FBI should have warned the Trump campaign about possible Russian influence rather than engaging what he said evolved into a "massive criminal conspiracy."
"People at the highest levels of the government took the law in their own hands," said Graham, a Republican.
Senator Dianne Feinstein, the panel's top Democrat, said the report had knocked down Trump's accusations that a "Deep State" of bureaucrats had worked to undermine his political prospects.
"Simply put, the FBI investigation was motivated by facts, not bias," she said.
Horowitz's work on the issue is not done. He said his office is examining whether FBI agents in New York improperly leaked information to Trump ally Rudy Giuliani in an effort to pressure then-FBI Director James Comey to re-open an investigation into Democratic presidential candidate Hillary Clinton's email use.
"What's proving to be very hard is the substance of the communications, but we can prove the contacts," Horowitz said.
Democrats say Comey hurt Clinton's candidacy when he said he was re-opening the investigation shortly before the election.
The FBI made at least 17 errors and omissions as it sought court approval to wiretap a Trump campaign adviser, Carter Page, Horowitz's report said.
"We are deeply concerned that so many basic and fundamental errors were made," Horowitz told the committee.
Page has not been charged with any crime.
Horowitz found that the FBI continued to rely on unverified information in its warrant applications even after a source told the agency that his statements had been mischaracterized.
The FBI also did not disclose to the Foreign Intelligence Surveillance Court (FISA), which approved the surveillance, that the information was funded by Trump's Democratic rivals, Horowitz said.
One FBI lawyer also altered information in a warrant application to hide the fact that Page had previously worked with a U.S. intelligence agency, which could have made it harder for the FBI to argue that he was a security risk, Horowitz said.
The investigation was taken over in May 2017 by former FBI chief Robert Mueller after Trump fired Comey.
Mueller's special counsel investigation detailed a Russian campaign of hacking and propaganda to sow discord in the United States and help Trump win. Mueller documented numerous contacts between Trump campaign figures and Moscow but found insufficient evidence of a criminal conspiracy.
(Reporting by Andy Sullivan; editing by Grant McCool)