Julia Hartley-Brewer called Lilly Allen "utterly bonkers" after the British singer described Donald Trump as a fascist in a heated Twitter row.
The argument was sparked by the talkRADIO presenter asking whether Mr Trump's UK state visit should really be cancelled over a petition and protests.
Allen replied to this, suggesting that big crowds can indeed bring change - pointing to the removal of Egyptian leader Hosni Mubarak during the Arab Spring in 2011.
The conversation then continued, with Allen saying the point of the petition was to state the British people's disapproval of Mr Trump's "fascist" regime, and pointing out that she is something of an expert on big crowds having played "many festivals."
The pair also disagreed about who started the conversation, and Julia eventually called Julia "bonkers" for her repeated messages.
View the tweets below