Donald Trump pressed the Ukrainian president to work with the US attorney general to investigate his political rival Joe Biden, a damning White House memo revealed on Wednesday, raising the stakes in an acrimonious and polarising impeachment inquiry.

Democrats said the US president’s conversation with Volodymyr Zelenskiy detailed in the five-page rough “transcript” was a devastating betrayal of his country that merited their investigation, while Republicans claimed it showed no quid pro quo and offered complete vindication.

The disclosure came a day after Nancy Pelosi, the House speaker, announced an official impeachment inquiry following a whistleblower’s complaint regarding alleged violations by Trump, setting the stage for a long and rancorous fight in the run-up to next year’s presidential election.

Some observers expressed surprise that the White House had agreed to release such a damaging memo detailing the 30-minute call between Trump and Zelenskiy on 25 July. Though not a verbatim transcript, it showed that, after being congratulated on his victory in the Ukrainian election, Zelenskiy thanked the US for its military support and said he was almost ready to buy more American weapons.

Trump replied “I would like you to do us a favor, though” and went on discuss possible joint investigations. Later in the conversation, he told Zelenskiy he should work with Trump’s lawyer, Rudy Giuliani, and the US attorney general, William Barr, to look into unsubstantiated allegations that Biden, the former vice-president, helped remove a Ukrainian prosecutor investigating his son, Hunter, who was on the board of a Ukrainian gas company.

Trump said: “There’s a lot of talk about Biden’s son, that Biden stopped the prosecution and a lot of people want to find out about that so whatever you can do with the attorney general would be great. Biden went around bragging that he stopped the prosecution so if you can look into it.”

He added: “It sounds horrible to me.”

The previously unknown connection to Barr was a potentially grave development for Trump because it shows he sought to involve the US government with a foreign country to look for dirt on a potential election rival. There is no evidence of wrongdoing by Biden, currently a frontrunner for the 2020 Democratic nomination for president.

Trump and Zelenskiy came face to face on the sidelines of the UN general assembly on Wednesday and the awkward body language was plain for all to see. The Ukrainian president told reporters: “I think you read everything. I think you read text. I’m sorry, but I don’t want to be involved to democratic open elections of USA. No.”

Zelenskiy added: “Sure, we had, I think, good phone call. It was normal. We spoke about many things, and I – so I think and you read it that nobody pushed me.”

Trump commented: “In other words, there was no pressure and you know there was no pressure.”

But Democrats seized on the memo’s contents, saying it showed Trump used his powers not for America’s national security but to hurt Biden and help his own re-election.

Biden said in a statement: “It is a tragedy for this country that our president put personal politics above his sacred oath. He has put his own political interests over our national security interest, which is bolstering Ukraine against Russian pressure.

“It is an affront to every single American and the founding values of our country. This is not a Republican issue or a Democratic issue. It is a national security issue. It is a test of our democratic values.”

Pelosi condemned Trump for using taxpayer money to “shake down” other countries for the benefit of his campaign. “The transcript and the justice department’s acting in a rogue fashion in being complicit in the president’s lawlessness confirm the need for an impeachment inquiry,” she said. “Clearly, the Congress must act.”

Adam Schiff, the chair of the House intelligence committee, told reporters: “The notes of the call reflect a conversation far more damning than I and many others had imagined.”

He added: “This is how a mafia boss talks. And it’s clear that the Ukraine president understands exactly what is expected of him.”

But the alternative realities that have pervaded American politics for the past three years were still in evidence. Trump and his allies sought to paint a very different picture, insisting that the memo proved his innocence.

The Trump re-election campaign fired off emails seeking to raise funds off the “smear job” by soliciting donations for an “Official Impeachment Defense Task Force”.

Brad Parscale, Trump’s 2020 campaign manager, suggested that the move to impeach will energise Trump’s supporters and boost his chance of re-election. He said: “Because of their pure hatred for President Trump, desperate Democrats and the salivating media already had determined their mission: take out the president.”

Parscale went on: “The facts prove the president did nothing wrong. This is just another hoax from Democrats and the media, contributing to the landslide re-election of President Trump in 2020.”

There was little sign of Republicans breaking ranks, meaning that even if Trump is impeached by the House, he would not be convicted and removed from office by the Republican-controlled Senate. Lindsey Graham of South Carolina, a Trump loyalist, said: “Impeachment over this? What a nothing (non-quid pro quo) burger. Democrats have lost their minds when it comes to President Trump.”

Speaking on the floor of the Senate, John Cornyn of Texas said: “This is a continuation of the election in 2016 where our Democratic friends can’t believe that Hillary Clinton lost the election to Donald Trump.”

One of the few dissenting voices was Senator Mitt Romney, the Republican nominee for president in 2012. Speaking at the Atlantic magazine festival in Washington, he said of the transcript: “My reaction was the same as I had a few days ago, which is this remains deeply troubling and we’ll see where it leads. But my first reaction is it’s troubling.”

Trump had recently confirmed that he ordered the freezing of nearly $400m in military aid to Ukraine a few days before the call. He claimed it was because the US was paying more than its fair share rather than any threat of blackmail or a quid pro quo. The aid was eventually released under pressure from Congress.

The Ukraine scandal erupted after an intelligence community whistleblower came forward. Democrats have been demanding details of the whistleblower’s complaint, but the acting director of national intelligence, Joseph Maguire, has refused to share that information, citing presidential privilege. He is to testify before the House on Thursday.

On Wednesday it also emerged that the intelligence community’s inspector general told the acting director of national intelligence that the call could have been a federal campaign finance violation. But the justice department determined the president did not commit a crime after prosecutors reviewed a rough transcript.

The justice department also denied that Trump had sought to involve Barr in any attempt to inflict damage on Biden. “The president has not asked the Attorney General to contact Ukraine – on this or any other matter,” a spokesperson said. “The attorney general has not communicated with Ukraine – on this or any other subject. Nor has the attorney general discussed this matter, or anything relating to Ukraine, with Rudy Giuliani.”

The Guardian