A former senior adviser to US secretary of state Mike Pompeo will testify before three House of Representatives committees on Wednesday as the impeachment inquiry into president Donald Trump continues apace.

Michael McKinley, a long-term state department official, who resigned last week, will be questioned by the three Democrat-controlled committees conducting the impeachment inquiry.

His testimony may shed light on the decision by Mr Pompeo to recall former US ambassador to Ukraine Marie Yovanovitch from the position earlier this year. Testifying before the committees last Friday, Ms Yovanovitch said she believed that her removal was based on “unfounded and false claims by people with clearly questionable motives”.

Mr McKinley is the latest senior figure to testify before the House committees, which are investigating Mr Trump’s links with Ukraine and his call for the Ukrainian government to investigate former vice-president Joe Biden.

On Tuesday, George Kent, deputy assistant secretary of state in charge of Ukraine policy, was questioned by politicians. It is understood that Mr Kent – who appeared despite an order from the state department not to do so – said he had raised concerns about Mr Trump and the efforts of the president’s personal lawyer Rudy Giuliani to encourage the Ukrainian government to investigate Mr Biden.

She said that former national security adviser John Bolton instructed her to inform White House lawyers about Mr Giuliani’s apparent efforts to encourage the Ukrainian president to investigate the activities in Ukraine of Mr Biden and his son, Hunter.

According to reports of Ms Hill’s testimony, Mr Bolton was said to be alarmed by the activities of Mr Giuliani, White House chief of staff Mick Mulvaney and US ambassador to the European Union Gordon Sondland.

Mr Bolton, who left the White House last month after a split with the US president, is now likely to be a subject of interest to investigators, and could be subpoenaed to testify before the committees.

Key role Mr Sondland, who was last week blocked by the White House from testifying to the committees, is due to testify on Thursday. The 62-year-old former hotelier played a key role in efforts to connect Mr Trump and Ukrainian president Volodymyr Zelenskiy, including attending the former comedian’s inauguration as Ukrainian president in May.

As Democrats continued their investigation, Hunter Biden gave his first interview since Mr Trump accused him and his father of corrupt activity over their activities in Ukraine.

In an interview with ABC News broadcast on Tuesday, Hunter Biden (49) said he did nothing “improper” but admitted to “poor judgment” when he joined the board of the Ukrainian gas company Burisma during his father’s tenure as vice-president.

“Did I make a mistake? Well, maybe in the grand scheme of things, yeah,” Mr Biden said in the interview. “But did I make a mistake based upon some ethical lapse? Absolutely not.”

He added: “I don’t think that there’s a lot of things that would have happened in my life if my last name wasn’t Biden.”

His comments come days after he announced that he would not work for foreign companies if his father becomes president.

Mr Trump referred to the interview – which was broadcast hours before Tuesday night’s Democratic presidential debate – in a tweet. “Hunter Biden was really bad on @GMA [Good Morning America]. Now Sleepy Joe has real problems!”