“If anything, staying within the advertising rules has taken a disproportionate amount of time and effort to interpret and comply with,” said Yes Vote spokesperson Deborah Morris-Travers. “We’ve had extensive and regular consultations with the Chief Electoral Office on how to interpret the advertising rules, and the clear advice has been that the Yes Vote campaign, branded as such, is a distinct campaign in itself.

“Our advice has been that the spending cap applies to distinct campaigns, as opposed to the possibility that one or more groups might mount their own campaigns.

“Far from flouting the regulations, we have tried to be scrupulous about following them, which makes today’s story doubly disappointing,” Ms Morris-Travers said.