Former Vice President Joe Biden defended himself and his son during the fourth Democratic debate saying they did nothing wrong.

Biden who was the frontrunner in the Democratic field for 2020 elections has slipped down after being embroiled in the Ukraine controversy. President Donald Trump and the GOP leaders have accused the former vice president and his son Hunter Biden of carrying out illegal dealings in Ukraine.

Trump pushing Ukraine and China to investigate the matter kickstarted the entire impeachment investigation.

Biden, speaking at the fourth Democratic debate at Ohio defended himself and his son saying they had done nothing wrong.

"Look, my son did nothing wrong. I did nothing wrong," Biden said, after being pushed by the commentators on the debate to comment on Hunter's interview with ABC news.

Hunter said that he used poor judgment in choosing to serve the board of Ukrainian gas company, which has now become a liability for his father.

"Was it poor judgement to be in the middle of something that is-- it's a swamp, in many ways? Yeah," he told ABC News.

He joined the board of a gas company in Ukraine more than half a decade ago when his father was the Vice President during the Obama government, trying to control corruption in Ukraine. At this time the owner of the gas company, Mykola Zlochevsky, was under criminal investigation. 

According to the accusations made by the Trump camp, Joe intervened to fire a top Ukraine prosecutor to quash the probe against Zlochevsky. However, Biden maintained that he has only carried out the policies of the United States. 

"I carried out the policies of the United States government which was to root out corruption in Ukraine, and that's what we should be focusing on," Joe said at the debate on Tuesday night. "[Trump] knows if I get the nomination, I will beat him like a drum."

Biden promised at the debate that if he were to be the President, no members of his family will engage in foreign deals. He also said that he never discussed Ukraine matter with his son, but was contradicted by his son when he admitted he had discussed Ukraine with his father once.

Tuesday's debate was Joe's chance to repel the allegations made against him and further cement his position, however, he mounted a weak response and was widely regarded as one of the losers in the debate.

Democratic White House hopeful Joe Biden is pushing back fiercely against US President Donald Trump, who has repeatedly criticized the former vice president and accused him, without evidence, of being involved in corruption in Ukraine Democratic White House hopeful Joe Biden is pushing back fiercely against US President Donald Trump, who has repeatedly criticized the former vice president and accused him, without evidence, of being involved in corruption in Ukraine Photo: AFP / Robyn Beck