Boris Johnson is under more pressure after a video showing Steve Bannon talk about their relationship cast his previous denials of any association into doubt.
Last year, Mr Johnson dismissed any relationship with Mr Bannon as “lefty delusion” – but footage shot in July 2018 suggests the pair have been in contact.
In the video, which was unpublished material for documentary The Brink, Bannon is heard saying: “Today we are going to see if Boris Johnson tries to overthrow the British government. He’s going to give a speech in the Commons.”
He continues: “I’ve been talking to him all weekend about this speech. We went back and forth over the text.”
Mr Bannon talks about how they initially spoke over the phone but that it was “easier” to continue over text.
He claims his advice was to draw on the same themes touched upon in a June 2016 speech for the Leave campaign ahead of the Brexit referendum.
The Observer reports a spokesman for Mr Johnson said: “Any suggestion that Boris is colluding with or taking advice from Mr Bannon or Nigel Farage is totally preposterous to the point of conspiracy.”
He said last year: “I consider Boris Johnson someone who understands the physics in the ebb and flow of events. Those individuals are rare.”
“I’m not sure Boris is using the Trump playbook so much as giving the people what they want – authenticity,” added Mr Bannon.
“Boris just needs to be Boris – true to his nature and his calling – and I think he has potential to be a great prime minister, not a good one.”
Boris Johnson is currently the clear favourite to be the next prime minister.