Washington, Jul 12 (IANS): Republican Senator Mitt Romney has slammed President Donald Trump's decision to commute the prison sentence of his long-time political confidant Roger Stone.

"Unprecedented, historic corruption: an American President commutes the sentence of a person convicted by a jury of lying to shield that very President," Romney, one of the first Republican members on the Capitol Hill to comment on the issue, said in a tweet on Saturday.

Trump commuted Stone's 40-month prison sentence on Friday, four days before the latter was due to report to prison on July 14.

Stone, who has maintained his innocence and tried to appeal his conviction, was the last of six Trump associates to be charged in connection with former Special Counsel Robert Mueller's investigation into the Trump campaign's contacts with Russia that dogged the President's first two years in office.

Mueller did not find evidence to charge Trump campaign associates with conspiring with Russia to interfere in the 2016 election, but found that the campaign welcomed Moscow's interference efforts.

Justice Department leadership moved to reduce Stone's sentencing recommendation in February in a highly controversial move, leading all four career prosecutors working on his case to quit.

Stone was convicted last November by a jury in Washington, D.C., of all counts he was charged with, including lying to Congress in connection with its separate investigation into Russian interference, witness tampering and obstructing an official proceeding.

Claiming that Stone was "a victim of the Russia Hoax", Trump said in a lengthy statement granting his long-time ally clemency that Stone should not be pursued because prosecutors found no evidence proving that the Trump campaign colluded with Russia, Xinhua news agency reported.

"The simple fact is that if the Special Counsel had not been pursuing an absolutely baseless investigation, Stone would not be facing time in prison."

While Senate Judiciary Committee Chairman Lindsey Graham, a Republican, tweeted on Friday before the commutation that Trump's intervention "would be justified", Democrats railed against the presidential action, with Senate Minority Leader Chuck Schumer saying "equal justice under the law is once again being undermined by a lawless president who regards the Justice Department as his personal plaything".

Adam Schiff, who as chairman of the House Intelligence Committee, led the President's impeachment investigation last year, said that "with this commutation, Trump makes clear that there are two systems of justice in America: one for his criminal friends, and one for everyone else".