The US ambassador to the European Union has said Donald Trump instructed him and other envoys to work with his personal lawyer, Rudy Giuliani, on Ukraine policy.

Gordon Sondland told impeachment investigators he was “disappointed” by the directive.

Mr Sondland spoke to politicians for around 10 hours.

Some leaving the closed-door deposition said there were gaps in his testimony, and said Mr Sondland responded “I don’t know” and “I don’t recall” many times.

But they said it was enlightening and damning as the political appointee and Trump donor described Mr Giuliani’s role in US policy toward Ukraine.

“It is clear you have a shadow shakedown going on by Giuliani,” said Eric Swalwell, a Democratic member of the House intelligence panel.

“I think it is just important for the American people to understand Rudy Giuliani is Donald Trump and Donald Trump is Rudy Giuliani. If Rudy Giuliani is doing something it is because he’s the lawyer for Donald Trump, and lawyers don’t take actions that are not authorised by their clients.”

Mr Sondland’s testimony to three House committees was aimed at distancing himself from Mr Trump and Mr Giuliani’s efforts to pressure Ukraine into investigating Democratic rival Joe Biden and his son Hunter.

Mr Sondland said he was concerned the president delegated to Mr Giuliani foreign policy responsibilities that he thought belonged to the State Department.

But Mr Sondland followed Mr Trump’s instructions anyway.

He insisted that he played no role in encouraging investigations of Mr Biden, telling politicians he thought it improper to invite a foreign government to conduct criminal probes to influence American elections.

The ambassador was the latest in a series of witnesses to be privately interviewed by three House committees conducting the impeachment investigation.

He was one of several current and former Trump administration officials who have provided new information – and detailed diplomats’ concerns – about Mr Trump and Mr Giuliani and their attempts to influence Ukraine.

White House acting chief of staff Mick Mulvaney defended Mr Giuliani’s involvement in foreign policy, saying, “That’s the president’s call.” Even if some people don’t like it, he added, “it’s not Illegal. It’s not impeachable. The president gets to use who he wants to use.”

Mr Sondland’s attempts to stand apart from Mr Trump and Mr Giuliani are notable since, unlike other career civil servants who have testified in the impeachment inquiry, he is a hand-picked political appointee of the president who contributed $1 million to Mr Trump’s inaugural committee.

His appearance was especially anticipated since the text messages and other witness testimony place him at the centre of a foreign policy dialogue with Ukraine that officials feared circumvented normal channels and that is now at the centre of the impeachment inquiry.

In prepared remarks obtained by the Associated Press, Mr Sondland aimed to untether himself from any effort by the Republican president or Mr Giuliani to have a political rival investigated, joining other current and former administration officials who have communicated to Congress misgivings about the administration’s back channel dealings with Ukraine.

But Mr Sondland’s pivotal role in the dialogue, including discussions about a quid-pro-quo in which Ukraine’s president would get a coveted White House visit in exchange for satisfying Mr Trump’s push for corruption-related investigations, made some Democrats sceptical that he was not more closely involved.

“For purposes of the impeachment inquiry, it really doesn’t matter whether Sondland was a knowing participant in this scheme or if he was an unwitting pawn,” said Ted Lieu as he left the deposition.

“He was still executing the policies of Rudy Giuliani and Rudy was following the orders of the president.”