US attorney general William Barr has said the investigation into Russian meddling in the 2016 election began “without any basis” and was intended to “sabotage the presidency” of Donald Trump.

Mr Barr told Fox News Channel’s Laura Ingraham that Mr Trump had “every right to be frustrated” with the probe which led to his impeachment “because I think what happened to him was one of the greatest travesties in American history”.

The FBI launched its counterintelligence investigation into ties between the Trump campaign and Russia “without any basis”, the attorney general added.

He said: “Even more concerning, actually, is what happened after the campaign, a whole pattern of events while he was president. To sabotage the presidency, and I think that — or at least have the effect of sabotaging the presidency.”

Mr Barr has appointed a US attorney to lead a criminal investigation into the origins of the probe led by former FBI director Robert Mueller.

Mr Barr, serving in his second stint as attorney general, has sought to paint himself as an independent leader who would not bow to political pressure.

But Democrats have repeatedly accused him of acting more like the president’s personal attorney than the attorney general.

Mr Barr has proved to be a largely reliable Trump ally and defender of presidential power.