US President Donald Trump's decision to pardon Indian-American conservative commentator Dinesh D'Souza is being strongly criticised here, with New York Attorney General Barbara Underwood describing it as thwarting the cause of justice.

Trump yesterday pardoned D'Souza, who was sentenced to five years of probation in 2014 for violating federal campaign laws.

"Trump's latest pardon makes crystal clear his willingness to use his pardon power to thwart the cause of justice, rather than advance it. By pardoning Dinesh D'Souza, President Trump is undermining the rule of law by pardoning a political supporter who is an unapologetic convicted felon," Underwood said in a statement.

The president, who has never met D'Souza or spoken to him, last night called him on the phone to inform him about his decision. Trump said he spoke to D'Souza "for three minutes last night...He almost had a heart attack.

Referring to previous pardons by Trump, Underwood said "we can't afford to wait to see who will be next."

Underwood called on lawmakers to act now to close New York's double jeopardy loophole and ensure that anyone who evades federal justice by virtue of a politically expedient pardon can be held accountable if they violate New York law.

In April, the Attorney General's office sent a letter to state lawmakers urging them to close a loophole in New York's double jeopardy law. Closing the loophole would ensure that individuals who broke New York law could not evade accountability for any state crimes as a result of a strategically-timed pardon by the president.

The New York Times, in a scathing editorial on Trump's pardon of D'Souza, said the president "uses whatever power he has to attack the people he feels have wronged him, and he will do what he feels he must to protect himself. For him, pardons are a means of vengeance."

The editorial titled "Dinesh D'SouzaIJ ReallyIJ said the message that can be taken from Trump's executive clemency is that "maybe the president is sending a signal of loyalty and reassurance to friends and family members who may soon find themselves facing similar criminal charges in connection with the special counsel's Russia inquiry."