The lawyer spoke after Manafort was sentenced to 47 months in prison in the US state of Virginia over bank and tax fraud related to his work in Ukraine.
"Most importantly what you saw today is the same thing that we had said from day one — there is absolutely no evidence that Paul Manafort was involved in any collusion with any government official from Russia," Downing said on Thursday.
Manafort had faced up to 25 years in prison for tax and bank fraud, and additional time for conspiracy counts including those related to work he did for the Ukraine government.
The judge also pointed out that the sentence is not related to the Russian investigation.
Manafort is also facing sentencing in a separate case in Washington, DC on March 13 on one count of conspiracy against the United States and one count of conspiracy to obstruct justice.
Special Counsel Robert Mueller has been investigating claims that Russia meddled in the 2016 US presidential election, as well as allegations of collusion between Trump's campaign team and Moscow.
Russia has repeatedly denied interfering in the election, saying the allegations were made up as an excuse for the defeat of Trump's campaign opponent as well as to deflect public attention from actual instances of electoral fraud and corruption. The claims of collusion have also been repeatedly dismissed by both Moscow and US President Donald Trump, who has called Mueller's probe a "witch hunt."