There is now “more than circumstantial evidence” the member's of Donald Trump’s campaign team colluding with Russia to disrupt the presidential election, a leading Democrat has claimed.

Adam Schiff, who sits on the House Intelligence Committee, told US broadcaster MSNBC that there was evidence “very much worth of investigation”, but he refused to elaborate on what that might be.

“I can tell you that the case is more than that,” the California congressman said. “And I can’t go into the particulars, but there is more than circumstantial evidence now.

“I don’t want to go into specifics, but I will say that there is evidence that is not circumstantial and is very much worthy of investigation, so that is what we ought to do.”

Asked by host Chuck Todd is he had “seen direct evidence of collusion”, he refused to expand on his previous statement.

His comments came within days of FBI director James Comey's admission that the Bureau was looking into both Russia’s alleged interference with the 2016 election and also possible links between Moscow and members of Donald Trump’s campaign team.

Mr Schiff questioned Mr Comey when he appeared before politicians earlier this week, although one prominent newspaper described his performance as “more labradoodle than Doberman”.

Other congressional committees also are investigating a possible Russian connection mostly behind closed doors.

The US government alleged last summer that Russian intelligence had tried to interfere with the presidential election, in an apparent attempt to help Mr Trump. This included hacking into the emails of senior members of Hillary Clinton’s team and the Democratic National Committee.

In late December, Mr Obama expelled 35 Russian diplomats in punishment for the alleged interference. Vladimir Putin surprised many by deciding not to reciprocate.