Corbyn's team declined to comment on how Abbott ended up sending messages pretending to be from their candidate without their express permission.

A spokesperson insisted that the campaign is "not making any comment about that".

However it is understood that they were surprised when Labour supporters received the message on Wednesday afternoon, which appeared to suggest Corbyn and Abbott were running on a formal joint ticket.

Diane Abbott, a long-term ally of Corbyn, told BuzzFeed News that she had operated under the understanding "that Jeremy authorised the text personally" and that is why her team sent messages in his name.

"Jeremy has provided quotes in support of me which we have used extensively in printed material," she added by way of evidence for his backing for her candidacy.

"He has also done three meetings in support of my campaign. They include at a fundraiser and speaking at two rallies. The most recent rally was this Tuesday where Jeremy got up in front of 800 people and said he was supporting me."