US President Donald Trump has called former FBI director James Comey’s decision to reveal details their conversations as “cowardly” and says the leak could have legal consequences.

Mr Comey told the Senate Intelligence Committee in testimony last week that after Mr Trump fired him on May 9, he asked a friend to leak his documentation of a meeting with the President to the press in the hope of prompting the appointment of a special prosecutor to investigate Russian election interference.

Mr Comey said he felt it was necessary to take notes of his meetings and conversations with President Trump because he feared the president would lie about what took place.

“I believe the James Comey leaks will be far more prevalent than anyone ever thought possible. Totally illegal? Very ‘cowardly!'” Trump said on Twitter.

I believe the James Comey leaks will be far more prevalent than anyone ever thought possible. Totally illegal? Very 'cowardly!'

— Donald J. Trump (@realDonaldTrump) June 11, 2017

The leaks have created a political firestorm over whether President Trump attempted to pervert the course of justice by pressuring Mr Comey to drop an investigation into contacts between Russian officials and former national security adviser Michael Flynn.

Mr Comey says he believes President Trump fired him because of the Russia investigation, and Mr Trump himself cited “this Russia thing” as a motivating factor for his decision to sack Mr Comey during an interview with broadcaster NBC that aired last month.

Mr Trump’s fellow Republicans have pressed the President to reveal whether he has tapes of his private conversations with Mr Comey and provide them to Congress if he does.

“I don’t understand why the President just doesn’t clear this matter up once and for all,” Republican senator Susan Collins said, referring to the existence of any recordings.

Senator Collins, who is also a member of the Senate Intelligence Committee investigating the Trump election campaign’s links to Russia, described Mr Comey’s testimony as “candid” and “thorough” and said she would support a subpoena if needed to access any tapes.

“[Mr Trump] should voluntarily turn them over,” she added.

The White House has so far avoided questions about whether conversations relevant to the Russia investigation have been recorded, as has the President.

Pressed on the issue Friday, Mr Trump said: “I’ll tell you about that maybe sometime in the very near future.”

– With agencies