Former CIA director John Brennan said Tuesday he was concerned about the number of contacts between Americans involved with the Trump campaign and the Russians last year.

During his first public remarks since he left his post in January, Brennan told lawmakers he was so concerned about Russia's efforts to interfere in the 2016 election and recruit Americans that he convened a group of officials from the CIA, FBI and National Security Agency in late July to focus exclusively on the issue.

'My radar goes up when I see certain things.' — John Brennan, former CIA director

"My radar goes up when I see certain things," Brennan said, noting, throughout his career, he has studied Russian intelligence activities including "how they've been able to get people, including inside CIA, to be treasonous."

"Frequently, individuals who go along a treasonous path do not even realize they are along that path until it gets to be a bit too late," he said.

Republicans on the House intelligence committee pushed Brennan about whether there was evidence of collusion between Russia and the Trump campaign, a point President Donald Trump has tried to enlist allies to quash. Brennan said the CIA focuses on intelligence, not "evidence," and said he was not able to answer that question.

Brennan said that when he was CIA director he shared classified information with Russia and other nations about threats related to terrorism. But Brennan told the committee that President Donald Trump would have violated protocol if he shared such information with Russian officials in the Oval Office spontaneously. He said such classified information typically gets shared through intelligence channels, not visiting diplomats. 

He also said that before sharing such classified intelligence with foreign partners, the U.S. would go back to the intelligence partner that provided the information to make sure what was shared would not compromise operatives. 

USA-TRUMP/RUSSIA

Former CIA director John Brennan testifies before the House Intelligence Committee on Russian 'active measures' during the 2016 U.S. election campaign, in Washington, May 23. (Kevin Lamarque/Reuters)

Brennan said he thinks Russia co-operates with WikiLeaks through middlemen, using intermediaries to work with the anti-secrecy group. The website released material hacked from email accounts of the Democratic National Committee and Hillary Clinton campaign officials during last year's presidential campaign.
 
He said that if someone tracks WikiLeaks' releases over time, it's clear that they are often timed to coincide with certain events or to undermine national security. Brennan said that Russian protests that they are not working with WikiLeaks and WikiLeaks protests that they are not working with the Russians are both "disingenuous." 

Brennan's statements about the number of contacts between associates of the Trump campaign and the Russians again put details about the Trump campaign's contacts with the Kremlin into the spotlight as reports emerged that Trump had asked his national intelligence director and NSA chief to state publicly there was no evidence of collusion before investigations into the matter were complete.

Director of National Intelligence Dan Coats told a Senate panel Tuesday he would not comment on the reports.

Brennan's testimony came the day after Trump's former national security adviser, Michael Flynn, invoked his constitutional right against self-incrimination in response to a subpoena from the Senate intelligence committee, which, like the House intelligence committee, is conducting an investigation into the Russian meddling and possible co-ordination with the Trump campaign. The Senate intelligence committee asked Flynn and three other Trump campaign associates for documents, including lists of meetings he had with the Russians during the campaign.

The FBI is also conducting a counterintelligence investigation into Russia and the Trump campaign.

Trump National Security Advisor

Flynn invoked his constitutional right against self-incrimination in response to a subpoena from the Senate intelligence committee. (Carolyn Kaster/Associated Press)

Former acting attorney general Sally Yates previously told Congress that the Justice Department was concerned that Flynn was compromised by the Russians and could be vulnerable to blackmail as Trump's national security adviser because of misleading statements he made to the vice president about his communications with the Russian ambassador to the U.S. Trump in February fired Flynn over the misleading statements, but he has since defended Flynn and his integrity.

On Monday, Congressman Elijah Cummings, the senior Democrat on the House oversight committee, cited inconsistencies in Flynn's disclosures to U.S. investigators during his security clearance review in early 2016.

Cummings said in a new letter that Flynn appeared to lie about the source of a $33,000 payment from Russia's state-sponsored television network, failed to identify foreign officials with whom he met — including Russia's President Vladimir Putin — and glossed over his firing as chief of the Defence Intelligence Agency during the Obama administration. Cummings asked the committee's chairman, Jason Chaffetz, a Republican from Utah, to subpoena the White House for documents related to Flynn.

Flynn's attorney, Robert Kelner, declined to comment on the new assertions by Cummings.