US National Intelligence Director Tulsi Gabbard launched a new attack on former President Barack Obama this week, alleging that he conspired to undermine Trump’s 2016 presidential victory by using false intelligence purporting to show Russian interference in Trump’s favour.

The administration’s claims are overblown, but newly declassified information provides some messy details about a January 2017 intelligence assessment of Moscow’s election interference.

"Yes, they tried to influence it. No, unless we poll every voter as to why they voted, we can’t tell you if that worked," Susan Miller said.

The long-simmering feud between President Trump and former President Obama erupted this week after Trump accused his predecessor of treason, a startling escalation in the fight between the two leaders.

Senate Judiciary Committee members seek special counsel to investigate declassified intelligence by DNI Gabbard about Obama-era Russian interference claims.

Hours after Trump falsely accused Obama of trying to rig the 2016 election, the ex-president’s office said it had no choice but to publicly refute the claim.

"We definitely had the intel," Susan Miller, who helped oversee the 2017 intelligence assessment of Russia's efforts in the 2016 election, told NBC News.