"He'd like to get foreign help to win elections," Biden said of Trump at a private California fundraiser, according to a pool report, marking his strongest comments to date on the Ukraine scandal.

The Democratic presidential candidate asserted there hasn't been "one shred of evidence" showing wrongdoing by his family, according to the report. "There's nothing anybody in my family did wrong ... at all."

While at the fundraiser, the former vice president quoted an excerpt of a stunning whistleblower complaint that was released earlier on Thursday, according to the report. The complaint alleges Trump abused his official powers "to solicit interference" from Ukraine in the upcoming 2020 election, and that the White House took steps to cover it up. Trump has denied any wrongdoing.