Quoting a confidential informant, Rep. Elijah Cummings, the top Democrat on the House Oversight and Government Reform Committee, wrote that Alex Copson, managing partner of ACU Strategic Partners, told the informant that Flynn would see that the sanctions on Moscow were "ripped up".
According to the whistleblower, Copson said, "Mike has been putting everything in place for us". Mr. Cummings said that Mr. Gowdy should subpoena Mr. Flynn, Mr. Copson and four others to testify before the panel.
The episode indicates that Trump officials had planned to jettison sanctions that the Obama administration had imposed on Russian Federation.
Flynn pled guilty last week to lying to the Federal Bureau of Investigation regarding conversations with Russians.
During their conversation, Mr. Copson informed the whistleblower that he "just got this text message" from General Flynn that the project was "good to go" and directing Mr. Copson to contact their business colleagues to "let them know to put things in place".
"I believe the American people want Congress to hold President Trump and his administration accountable", Cummings wrote, "and they are exhausted of Republicans in Congress putting their heads in the sand when faced with credible allegations of grave abuses".
Former National Security Advisor Michael Flynn told a former business associate "within minutes" of President Donald Trump being sworn in on Inauguration Day that economic sanctions against Russian Federation would be "ripped up" once Trump gets into office, according to a whistleblower.
Gowdy did not immediately respond to a request for comment from CNBC.
Perhaps most intriguingly of all, Cummingswrites that he told Special Counsel Robert Mueller's team about all this some time ago - and that they asked him to delay publicly revealing this information "until they completed certain investigation steps".
Cummings said he had found the unnamed informant to be "authentic, credible and reliable", and offered to produce the person for Gowdy. Mr Copson was described by the whistle-blower as responding, "I couldn't be better", and that he was "going to celebrate today".
The whistleblower also says that Flynn assured Copson that US sanctions on Russian Federation that could block the nuclear project would be "ripped up" once Trump was inside the White House.
ACU Strategic Partners paid for Flynn to travel to Israel and Egypt in 2015 to promote the nuclear project, paying him a fee of $25,000, according to a letter Copson sent the committee. "But the exceptionally troubling allegations in this case - combined with ongoing obstruction from the White House and others - have made this step necessary".
Mr Copson explained that Flynn was making sure that sanctions were going to be "ripped up" as one of the first orders of business and this would allow money to start flowing to the project.
Copson showed the witness the text on his phone.
Mr Cumming added, "If you agree to protect the individual's identity, this whistle-blower will speak with you directly so you can verify the information in this letter".