Senator Dianne Feinstein says the "most notable part of [the Kavanaugh report] is what's not in it".
The FBI's report into Brett Kavanaugh was released to Senators Friday morning (NZ time), but has been slammed by Ms Feinstein and Senate Minority leader Chuck Schumer.
The report will not be made public.
Mr Kavanaugh is accused of sexually assaulting Dr Christine Blasey Ford at a party in 1982.
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"It looks to be a product of an incomplete investigation that was limited, perhaps by the White House. I don't know," Ms Feinstein said.
"Democrats agreed that the investigation's scope should be limited. We did not agree that the White House should tie the FBI's hands."
Mr Schumer told media that before the investigation Democrats had fears over the parameters of the investigation.
"Having received a thorough briefing on the documents, those fears have been realised," Mr Schumer said.
President Donald Trump has also weighed in on the investigation via Twitter.
"This is now the 7th time the FBI has investigated Judge Kavanaugh. If we made it 100, it would still not be enough for the Obstructionist Democrats," Mr Trump said.
Senate Judiciary Chairman Chuck Grassley issued a statement saying there was nothing "we didn't already know" in the investigation.
"It's time to vote. I'll be voting to confirm Judge Kavanaugh."
Newshub.
