Democrats on the House Intelligence Committee began leaking information about Donald Trump Jr.'s interview last week while it was still going on, according to his lawyer.

In a stinging letter to committee members, attorney Alan Futerfas said Trump Jr. and his counsel were promised his interview would be 'kept strictly confidential and not discussed publicly unless and until the full committee voted to release the transcript.'

Futerfas cites tweets from CNN reporters and a paid contributor during the nearly 8-hour grilling as evidence that Democrats were secreting information to the press.

'[W]hile the interview was in progress, members of the Committee and/or their staff began selectively leaking information provided during the interview to various press outlets, most notably CNN,' he claims.

Donald Trump Jr. (pictured) and his lawyer are demanding an investigation into how information from his closed-door grilling by the House Intelligence Committee was leaked to CNN while it was still going on

Trump's lawyer points a finger at committee Democrats, led by California Democrat Adam Schiff, for the leaks

Trump Jr.'s December 6 interview started at 10:00 a.m. and ended just before 6:00 p.m.

He and his lawyers were required to surrender their cell phones for that entire stretch of time.

But at 1:01 p.m., a CNN reporter tweeted information about ths testimony.

'Don Jr. made case to House investigators that he did NOT tell his father about the June 2016 Trump Tower meeting, I'm told. Made similar case to Senate Judiciary staff in September,' wrote Manu Raju.

Just before 4:00, American Urban Radio Networks White House correspondent April Ryan, who doubles as a CNN contributor, tweeted a CNN article about that testimony.

CNN reported falsely on Dec. 7 that hacked emails from inside the Democratic National Committee were offered to Trump Jr. and his father before WikiLeaks published them; that turned out to be false, and Trump Jr.'s lawyer says committee Democrats were responsible

This tweet was sent by a CNN reporter three hours into the committee's eight-hour interview with Trump Jr.

A CNN paid contributor tweeted this story while the Trump Jr. grilling still had two hours to go

Raju tweeted at 4:29 p.m. about the same article, which described Trump Jr.'s response to that June 2016 Trump Tower meeting with Russian lawyer Natalia Veselnitskaya.

Futerfas noted that the committee's top Democrat, California Rep. Adam Schiff, and two other committee Democrats, had made media appearances to talk about the closed-door testimony.

Those were calculated efforts 'to discredit my client,' he wrote.

Futerfas wants the committee to launch an investigation into the leaks.

He also cited a December 7 CNN story that claimed Trump Jr. and his father, the president, were offered an advance look at hacked documents from inside the Democratic National Committee that WikiLeaks would later post online.

That report was based on sources who had seen the email, but CNN's reporters had not seen it themselves.

The network was forced to retract the story nine hours later after The Washington Post established that the 'offer' was a message from an insignificant Trump supporter – and sent after WikiLeaks published the material.

Futerfas claims that the ;clearly inaccurate' information was 'provided to CNN by memners or staff of this Committee.'

And in the intervening hours, while CNN touted its faulty 'exclusive,' he wrote, 'the individuals responsible for disseminating this inaccurate information to the press stood by and did nothing, all the while knowing that the story they had leaked was inaccurate.'

Schiff's office denied late Tuesday in a statement that he leaked any 'non-public' information about Trump Jr.

'Ranking Member Schiff and his staff do not leak classified or confidential information, and any disclosure of non-public information by the congressional committees undertaking investigations is singularly unhelpful,' the statement read.

'It is imperative that all investigations into Russia’s covert political interference campaign operate with appropriate discretion and refrain from publicizing information for short-sighted political gain.'