Biden calls for congressional inquiry into call in which Trump reportedly pressed Ukraine leader for damaging information.

Donald Trump had lashed back at his critics on Saturday, as questions swirled in the latest scandal to hit his White House and his target, Joe Biden, called for a congressional investigation of “an overwhelming abuse of power”.

“Nothing was said that was in any way wrong,” Trump said of a phone call with Volodymyr Zelenskiy in which, according to the Wall Street Journal, the US president asked “about eight times” that the Ukrainian leader investigate Biden’s son.

Biden is the frontrunner for the Democratic presidential nomination. His son Hunter was on the board of a Ukrainian gas company while his father was vice-president.

Trump already faces impeachment inquiries but the Ukraine call is reported to be related to an intelligence community whistleblower complaint about the president’s behaviour which is the subject of a standoff between the White House and Congress.

Washington is abuzz. Did the US president use or attempt to use military aid to Ukraine as leverage in seeking the investigation of a political rival?

Trump and Zelenskiy spoke on 25 July. About a month later, it was reported that $250m in military assistance to a country fighting Russian-backed separatists was being delayed after Trump requested a review.Nothing was said that was in any way wrong.

“The potentially most explosive issue here is whether the president essentially offered Ukraine a quid pro quo,” Richard Pildes, professor of constitutional law at New York University, told the Guardian.

“‘I’ll provide substantial US foreign aid if you provide damaging information concerning Joe Biden or his son.’”

Republican claims about the Bidens and Ukraine concern a visit by the then vice-president in March 2016. The country’s top prosecutor, Viktor Shokin, was fired soon after: an aim of the US, allies, the World Bank and the International Monetary Fund, which thought Shokin was turning a blind eye to corruption.

An investigation into the company for which Hunter Biden worked was dormant at the time. In May this year, Ukraine prosecutor general Yuriy Lutsenko told Bloomberg News “we do not see any wrongdoing” by the Bidens.

On Saturday, Trump used Twitter to allege it.

“The Fake News Media,” he wrote, “and their partner, the Democrat [sic] Party, want to stay as far away as possible from the Joe Biden demand that the Ukrainian Government fire a prosecutor who was investigating his son, or they won’t get a very large amount of US money, so they fabricate a story about me and a perfectly fine and routine conversation I had with the new President of the Ukraine.

“Nothing was said that was in any way wrong, but Biden’s demand … was a complete and total disaster. The Fake News knows this but doesn’t want to report!”

In the Oval Office on Friday, Trump was asked if he brought up Biden in his call with Zelenskiy.

“It doesn’t matter what I discussed,” he said, urging the media “to look into” Biden’s background with Ukraine.

Biden said that if the reports were true, “then there is truly no bottom to President Trump’s willingness to abuse his power and abase our country”. He also said Trump should release the transcript of his conversation with Zelenskiy.

Trump is using this because he knows I’ll beat him like a drum

On Saturday, in Iowa, Biden said the House of Representatives should investigate what “appears to be an overwhelming abuse of power”.

“To get on the phone with a foreign leader who is looking for help from the United States and ask about me and imply things – this is outrageous,” Biden said with visible anger.

“Trump is using this because he knows I’ll beat him like a drum and is using the abuse of power and every element of the presidency to try to do something to smear me.”

Biden’s campaign, meanwhile, used Trump’s attack in fundraising appeals.

The whistleblower’s complaint about Trump’s behaviour was filed on 12 August. The USintelligence inspector general called it “serious” and “urgent”. On Friday Trump dismissed it, insisting “it’s nothing … just another political hack job”.

“I have conversations with many leaders,” he said. “It’s always appropriate. Always appropriate. At the highest level always appropriate. And anything I do, I fight for this country.”

But questions remain about Trump’s view of Russia and relationship with Vladimir Putin, despite the conclusion of an investigation of Russian interference in the 2016 election. Special counsel Robert Mueller did not find evidence of a criminal conspiracy but did lay out links between Trump aides and Russians and multiple instances of potential obstruction of justice.

Russia annexed Crimea from Ukraine in 2014 and now backs separatists in the Donbass region. On Friday the Washington Post cited a former senior administration official who had “repeatedly discussed the issue with Trump” as saying the president thought military aid to Ukraine “was pointless and just aggravating the Russians”.

“The president’s position basically is, we should recognise the fact that the Russians should be our friends, and who cares about the Ukrainians?” the Post quoted the official as saying.

Ukrainian foreign minister Vadym Prystaiko told Ukrainian outlet Hromadske his country was not interested in taking sides in US politics, but said Zelenskiy had the right to keep his “long and friendly” conversation with Trump secret.

He also said US investigators had every right to uncover information, adding: “I know what the conversation was about and I do not think there was any pressure.”

In New York next week, Trump and Zelenskiy will meet on the sidelines of the United Nations.

In Washington, Adam Schiff, chair of the House intelligence committee, has said he will go to court to get hold of the whistleblower complaint.

On CNN on Thursday, Trump’s personal lawyer Rudy Giuliani was asked if he asked Ukraine to look into Hunter Biden. He said, “No, actually I didn’t,” but seconds later added: “Of course I did.” Trump was unaware of his actions, he said.

On Saturday, the former New York mayor claimed on Twitter: “Swamp Media been covering up Biden Family blatant trading on Joe’s offices for years.” (The Guardian, UK)

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