Donald Trump “knew exactly what was going on” during US efforts to pressure Ukraine into investigating his Democratic political rival Joe Biden, according to a key figure in the impeachment scandal.

Lev Parnas, who faces campaign finance charges in connection with the affair, broke his silence to contradict the President’s claims that he was in the dark about the alleged plot to dig dirt on the former vice-president.

“He was aware of all my movements,” Mr Parnas, an associate of Mr Trump’s personal lawyer, Rudy Giuliani, told MSNBC.

“I wouldn’t do anything without the consent of Rudy Giuliani, or the President. I have no intent, I have no reason, to speak to any of these officials,” he added.

“Who am I? They were told to meet with me. And that’s the secret that they’re trying to keep. I was on the ground doing their work.”

The new claims rocked Washington as the investigation into the President switches to the Senate today after the House of Representatives passed a resolution to submit articles of impeachment to the upper chamber for a trial.

Democrats claim the President demanded a quid pro quo by freezing a $391 million US military aid package to Ukraine and demanding an investigation into unsubstantiated corruption allegations about Mr Biden, one of the front-runners for the Democrat presidential nomination, and his son, Hunter, who had worked for a Ukrainian energy firm.

Mr Trump has denied charges of abuse of power and obstruction of justice as well as claims that he sought to pressure Ukrainian President Volodymyr Zelensky in a July 25 phone call. Mr Trump also denied knowing Mr Parnas and his associate Igor Fruman after they were charged with funnelling foreign money into US elections. They have both pleaded not guilty.

House Speaker Nancy Pelosi, said Washington was crossing “a threshold in history” by delivering the articles to the Senate.