On 18 January, Leave.EU co-chair Arron Banks wrote a letter to Vote Leave chief executive Matthew Elliott, criticising his refusal to merge with other Brexit groups and his suggestion of holding two referendums.
Banks believes the groups should unite forces, but said in the letter, which was also distributed to national media as a press release, that after initially showing an interest in this Vote Leave backed out of a merger.
When approached for comment by PRWeek, a spokesman for Vote Leave gave a statement that read, in full: "There will be no merger."
In another statement sent to press on 4 February, Banks said: "I am angry that this group is jeopardising this historic referendum through their dishonesty and unwillingness to embrace and work with all the Brexit groups. It's time they and the Conservative MPs associated with them decide if it's their career or their country which matters most to them, and then they can either fit in with the rest of us or quite frankly disappear."
When approached for comment by PRWeek, a spokesman for Vote Leave gave a statement that read, in full: "We wish them well."
On 5 February, articles appeared in The Times and The Guardian detailing a leaked internal email sent to Elliott and Vote Leave campaign director Dominic Cummings on Tuesday (2 February) from John Mills, Vote Leave's deputy chairman, in which he accuses Cummings of generating "ill-feeling" within the group.
In response to that, Banks issued a third attack on Vote Leave. In an "open letter from Arron Banks to Conservative MPs" sent to journalists and published on the Leave.EU website, Banks again refers to the tensions within the group, describing Elliott and Cummings as "two of the nastiest individuals I have ever had the misfortune to meet".
He also urges MPs to switch their support to Grassroots Out, claiming that Vote Leave "now has no real cross-party support".
When approached for comment by PRWeek, a spokesman for Vote Leave gave a statement that read, in full: "We wish Arron Banks well."
Leave.EU had previously criticised Vote Leave over its October announcement that Lord Lawson would lead the Brexit campaign, saying in a press statement: "The announcement that Lord Lawson is 'leading' the campaign to leave the EU is wrong. He's leading ‘a' campaign that is run by the 'Westminster bubble' from SW1."