Arthur Misty Thackeray bragged about how he and a colleague "covertly" attended a meeting of groups planning an anti-Ukip protest last week.
In an email to party members, Thackeray said he had taken the security "counter measures" ahead of a visit to Edinburgh by Ukip leader Farage, which attracted a large protest from groups opposed to his anti-immigration message.
Updating Ukip members on the "fantastic" event, Thackeray wrote: "As you will probably have seen there was a counter protest by far-left extremists aimed at intimidating our members.
"The threat posed by these violent groups is such that Nigel now has a personal security detail," he said.
"What you may not be aware of are the counter measures we deployed to address this protest, which included [treasurer] Rob Sale and I covertly attending the Radical Independence Campaign (RIC) planning meeting."
RIC said Thackeray and his friend had been clocked as soon as they walked in.
A spokesman said: "This just goes to highlight the bizarre nature of Ukip politics, which have no place in 2014."