Republicans called Kurt Volker to testify and he promptly shut down the right wing's biggest allegation against Joe Biden

• Kurt Volker, former US special representative to Ukraine, promptly shut down the GOP's allegations of corruption against former Vice President Joe Biden and his son, Hunter, in testimony before Congress. 
• The Republicans on the Intelligence Committee called Volker as one of their witnesses in the impeachment inquiry hearings, but he almost immediately shattered their main talking point.
• A major GOP talking point in defending Trump against the impeachment inquiry is that he was justified in asking Ukraine to investigate what he believed to be legitimate corruption on the part of Hunter Biden.
• But at the very beginning of his testimony, Volker strongly denounced the allegations of corruption against the Bidens as "self-serving," "not credible," and a "conspiracy."
• Visit Business Insider's homepage for more stories.

Kurt Volker, the former US special representative to Ukraine and a witness Republicans called to testify in the impeachment inquiry against President Donald Trump, promptly shut down the GOP's allegations of corruption against the Bidens.

Volker, who served as a diplomat in Ukraine, testified about his involvement in the Trump administration's efforts to pressure Ukraine to announce investigations into former Vice President Joe Biden and his son Hunter Biden, who served on the board of Burisma Holdings, a Ukrainian oil-and-gas company, from 2014 to 2019.

One of the biggest GOP talking points in defending Trump against the impeachment inquiry is that he was justified in asking Ukraine to investigate what he believed to be legitimate corruption on the part of Hunter Biden, and a coverup by his father in his capacity a vice president. 

But at the very beginning of his testimony, Volker immediately shattered that line of argumentation and denounced the allegations of corruption against the Bidens as "self-serving," "not credible," and a "conspiracy" pushed by Trump's personal attorney Rudy Giuliani. 

A debunked theory has led to the impeachment inquiry

The entire impeachment inquiry centers around Trump and the GOP's discredited claim that in his capacity as vice president, Biden tried to help his son by calling for the firing of Viktor Shokin, a prosecutor they say was investigating Burisma. 

Hunter, the eldest of Joe Biden's sons, served on Burisma's board providing legal advice and receiving a reported salary of around $50,000 a month. Burisma was the subject of an investigation from the Ukrainian prosecutor general's office into whether its founder Mykola Zlochevsky engaged in tax evasion, money laundering, and corruption.

Despite Trump and Giuliani's allegations, both US and Ukrainian government officials have confirmed there's no evidence that the Bidens did anything improper. 

Furthermore, Shokin was not even actively investigating Burisma at the time, and was denounced for being ineffective at his job.

The Journal and other outlets have reported that Shokin was widely accused of being soft on corruption and hindering investigations, including the one into Burisma - in essence, Biden, and much of the international community, urged Shokin's ouster because he was ineffective.

In fact, Shokin had hampered the investigation into Burisma long before Biden even stepped into the picture, according to the Wall Street Journal. Western diplomats also say he essentially shut down one such investigation into Burisma's founder in the UK by refusing to cooperate with authorities.