Senate majority leader Mitch McConnell has angrily hit out at critics who accused him of ignoring threats to US elections from Russia, claiming the “unhinged smears” amounted to “modern-day McCarthyism”.

Last week, Mr McConnell, a leading Republican ally of the president, blocked two measures designed to strengthen election security.

He claimed the bills, proposed by Democrats, were being tabled for the party’s political benefits.

But a number of people accused him of ignoring the threat of repeated Russian interference, with some even labelling him “Moscow Mitch”.

On Monday, Mr McConnell rejected the criticism in a speech on the floor of the Senate.

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“I was called unpatriotic, un-American and essentially treasonous by a couple of left-wing pundits on the basis of bold-faced lies,” he said.

“I was accused of aiding and abetting the very man I’ve singled out as an adversary and opposed for nearly 20 years - Vladimir Putin.”

He said his critics, among them the MSNBC television channel and some journalists at the Washington Post, were guilty of smears. “Welcome to modern-day McCarthyism,” he said.

The bills Mr McConnell blocked had been proposed by Democrats Chuck Schumer and Richard Blumenthal.

Mitch McConnell says Donald Trump 'is not a racist'

They called for them to be passed by unanimous consent; under the rules governing the upper chamber of Congress, any one senator can try to pass a bill, but equally any one senator can object.

One of the bills would require the use of paper ballots, while the other would require candidates, campaigns or family members to notify the FBI about any offers of assistance from foreign governments.

“Clearly this request is not a serious effort to make a law. Clearly something so partisan that it only received one single solitary Republican vote in the House is not going to travel through the Senate by unanimous consent,” Mr McConnell said.

Democrats were furious by his remarks, coming as they did, a day after former social counsel Robert Mueller had testified about alleged Russian interference in the 2016 election, and said the threat had not gone away. “They’re doing it as we sit here,” he said.

“These pundits are lying, lying when they dismiss the work that has been done,” Mr McConnell said on Monday.

“They’re lying when they insist I have personally blocked actions which, in fact, I have championed and the Senate has passed. They are lying when they suggest that either party is against defending our democracy.”

Joe Scarborough, an MSNBC broadcaster, who had been critical to the Senate Republican leader, responded to Mr McConnell’s remarks on Twitter.