Simpson also discussed the financing of Trump's golf courses around the world, questioning if he had "enough money to do this and that" saying "he would have had to have outside financial support of these things".
"We also increasingly saw that Mr. Trump's business career had evolved over the prior decade into a lot of projects in overseas places, particularly in the former Soviet Union, that were very opaque, and that he had made a number of trips to Russian Federation, but said he'd never done a business deal there", Simpson said.
President Donald Trump personally made the call to have Stephen Bannon not answer questions during testimony before a congressional committee investigating Russian election meddling earlier this week, according to a report.
"They don't, on their face, show Russian involvement", he replied, "but what they do show is enormous amounts of capital flowing into these projects from unknown sources and - or at least on paper it says it's from The Trump Organisation - but it's hundreds of millions of dollars".
Mr Simpson's findings are based on his suspicions based around Mr Trump's financial statements filed in Ireland and the United Kingdom and the property developer's alleged connections with Russian mafia figures.
Under oath, Simpson said: "As we pieced together the early years of (Trump's) biography, it seemed as if during the early part of his career he had connections to a lot of Italian mafia figures, and then gradually during the 90s became associated with Russian mafia figures".
Backlash: YouTube Faces Partner Rage Over Monetization Changes
YouTube says this verification process will be completed by mid-February in the USA and end of March for the rest of the world. These changes replace the previous policy that allowed any user with 10,000 views to apply for the YouTube Partner Program.
"And these golf course are just, you know, they're sinks".
His firm examined financial statements filed for Doonbeg in the Companies Registration Office in Dublin and the NY property developer's golf courses in Scotland, he said. "They don't actually make any money".
Later in the House Intelligence hearing, Republican Party Congressman Tom Rooney said the stories that Mr Simpson was telling were "fascinating". A lot of what I do is analyse whether things make sense and whether they can be explained.
"And that didn't make sense to me, doesn't make sense to me to this day". Russian Federation has denied the conclusions of United States intelligence agencies that it interfered in the 2016 election to help Mr Trump and Mr Trump denies any collusion.
"We saw patterns of buying and selling that we thought were suggestive of money-laundering", he continued.
Recently released testimony shows Fusion GPS founder was trying to steer the FBI away from further investigation of the Clintons while he was encouraging investigators to look into Trump. "They're very serious allegations, and, again, not one that this investigative committee has the resources to pursue, but one hopes that if there's anything to the allegations, those who live in the criminal realm, that is to say Special Counsel Bob Mueller, would be doing the investigation of those allegations if he feels that there's reason to do so".
"But it's not surprising the minority (Democrats) would focus on this given they've found absolutely no evidence of collusion".