Bannon and Johnson communicated privately during the former Trump adviser's recent trip to London, a source who spent time with the former Trump advisor during his trip told BuzzFeed News.
"I'm sure they weren't discussing the cricket scores," the source said, admitting that he wasn't certain what exactly the two men talked about.
Johnson, who had remained relatively low-key following his resignation, renewed his attacks on May's Brexit plans on Thursday, calling them unworkable and urging fellow Conservative Party lawmakers to "chuck Chequers," referring to the government white paper on Brexit agreed at the prime minister's country house.
"It is vassalage, satrapy, colony status for the UK. For the first time in a thousand years our laws will be made overseas, enforced by a foreign court," Johnson wrote in an op-ed for The Spectator magazine.
Johnson resigned from his post on July 9 over his disagreement with Theresa May's Brexit approach, which he said would leave the country too closely dependent on the European Union after London leaves the bloc. Brexit Secretary David Davis also resigned.
During his London trip, Bannon offered praise for Johnson and defended Tommy Robinson, a right-wing UK activist jailed for breaching the peace outside a UK courthouse in May for reporting on the trial of a child molestation case involving Muslim immigrants.