Rudy Giuliani, personal lawyer to US President Donald Trump, has left two unintended voicemail messages on a reporter's phone, NBC News reports.
In the calls, Mr Giuliani reportedly spoke about needing money and attacked Democratic presidential candidate Joe Biden.
Mr Giuliani has not yet commented on the calls.
Lawmakers demanded documents from Mr Giuliani earlier this month as part of the presidential impeachment inquiry.
In the past he publicly admitted asking Ukrainian officials to investigate widely debunked corruption allegations against Mr Biden.
Three Democratic-led committees are currently investigating whether President Trump tried to pressure Ukraine's president into investigating Mr Biden in exchange for military aid.
What did Giuliani say?
NBC investigative reporter Rich Shapiro says he received two voicemails from Mr Giuliani in the space of a month.
He described them as the result of "what is known, in casual parlance, as a butt dial".
A "butt dial" happens when someone unknowingly calls one of their contacts by accidentally applying pressure to their phone's buttons while it is in their pocket.
Mr Shapiro missed the first call, mid-afternoon on 28 September, because he was at a child's birthday party. He had interviewed Mr Giuliani for an article the day before.
For the entirety of the ensuing three-minute voicemail, the president's personal lawyer reportedly attacked Mr Biden and his family.
"Biden has been trading in on his public office since he was a senator," Mr Giuliani reportedly said to an unidentified man. In the conversation, he brought up the discredited allegations that Joe Biden, when vice-president, stopped an investigation in Ukraine to protect his son Hunter.
"He did the same thing in China. And he tried to do it in Kazakhstan and in Russia," Mr Giuliani reportedly added.
In the second voicemail, left on the night of 16 October, Mr Giuliani again recorded a conversation with an unknown man.
"We need a few hundred thousand," Mr Giuliani reportedly said at one point, in a conversation that Mr Shapiro says covered Bahrain and an unknown man named Robert.
Who is Rudy Giuliani?
Mr Giuliani was mayor of New York City from 1994 until 2001, and was in office during the 9/11 terror ttacks.
He was one of the candidates for the Republican presidential nomination in 2008, before withdrawing and backing eventual candidate John McCain.
Since April 2018, he has served as a lawyer for President Trump.
Mr Giuliani was present during Mr Trump's call to Ukrainian President Volodymyr Zelensky in July, which is the subject of the impeachment inquiry.
His own activities in Ukraine are also under investigation.