Altoona, Iowa (CNN) Joe Biden said Sunday that even though he was the last top-tier Democratic candidate to call for President Donald Trump's impeachment, "I'm the reason there is impeachment going on."

The former vice president lambasted Trump for asking foreign governments to investigate him and his son Hunter -- despite there being no evidence of wrongdoing on the part of either Biden -- at a forum in Iowa, saying that the President is leading the "most corrupt administration in modern American history."

"It's gotten so far now, if you don't move on it, then what do we say to the rest of the world about who we are?" Biden said. "What do you say about opening the gates and saying, 'Come on in, get involved in our elections?' What do you do?"

The 2020 Democratic presidential candidate also told reporters that his family and associates would not work for foreign companies if he is elected president, saying he would have an environment in the White House reminiscent of former President Barack Obama's administration.

"I can tell you now, if I am your president -- next president -- I'm going to build on the squeaky clean, transparent environment that we had in the Obama-Biden White House," he said.

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