Congress is determined to get access to US President Donald Trump’s calls with Russian President Vladimir Putin and other world leaders, the chairman of the House Intelligence Committee said on Sunday, citing concerns the Republican leader may have jeopardised national security.

“I think the paramount need here is to protect the national security of the United States and see whether in the conversations with other world leaders and in particular with Putin, the President was also undermining our security in a way that he thought would personally benefit his campaign,” Democrat Adam Schiff said on NBC’s Meet the Press.

Following a whistleblower complaint that Trump solicited a political favour from Ukraine’s President that could help him get re-elected, the lawmakers are investigating concerns Trump’s actions jeopardised national security and the integrity of US elections.

White House adviser Stephen Miller took up the attack on Sunday, accusing the whistleblower of being part of a “deep state” government conspiracy to foment opposition to Trump. “I know the difference between a whistleblower and a ‘deep state’ operative. This is a ‘deep state’ operative pure and simple,” he told Fox News Sunday.

Trump’s Republican supporters in Congress defended the President’s actions on Sunday TV news shows.

“I have zero problems with this phone call,” Senator Lindsey Graham said on CBS’s Face the Nation.

The whistleblower’s complaint was deemed credible by the inspector-general of the US intelligence community and the acting director of national intelligence told lawmakers the person “acted in good faith” and “did the right thing”.

The complaint said White House lawyers directed that an electronic summary of the call, which was released to the public on Wednesday, be moved from the place where such things are usually kept to a secret server reserved for covert matters.