Clive Lewis has now flat-out denied he registered a group of Labour leadership websites, just a day after he failed to fully distance himself from the internet addresses on Sunday night (26 February).

The former shadow business secretary, who quit Jeremy Corbyn's top team over Brexit, told The Guardian: "None of this is true. I haven't done this."

Lewis' latest comments come after he failed to deny that he had registered and other domains on 29 June 2016, following the Leave vote at the EU referendum on 23 June.

"A lesson from LBJ [US President Lyndon B Johnson] in how to smash an opponent," he told The Huffington Post UK.

"Legend has it that LBJ, in one of his early congressional campaigns, told one of his aides to spread the story that Johnson's opponent f**ked pigs.

"The aide responded: 'Christ, Lyndon, we can't call the guy a pigf**ker. It isn't true.' To which LBJ supposedly replied: 'Of course it ain't true, but I want to make the son-of-a-bitch deny it.'"

The development comes after John McDonnell claimed that Jeremy Corbyn faced "soft coup" from "elements" within the Labour Party and Rupert Murdoch's media empire.

But a spokesman for the shadow chancellor later said McDonnell wrote the article, published on Sunday, a week ago and stressed that he wanted to focus on party unity in the wake of the by-election results, which saw Labour retain Stoke-on-Trent Central but lose Copeland to the Tories.

Corbyn, meanwhile, has reportedly rejected an invitation to appear before the weekly meeting of Labour's parliament party in the House of Commons on Monday evening. The by-elections are expected to be among the main topics of conversation.