Rebecca Long Bailey, who is aiming to succeed Jeremy Corbyn as the left-wing candidate, and Angela Rayner, who could be her deputy

Allies of Angela Rayner are warning the leading Labour MP not to endorse the leadership campaign of Rebecca Long Bailey — despite the pair being tipped to run on a joint ticket.

Ms Long Bailey and Ms Rayner, who are flatmates, are widely expected to run for Labour’s leadership and deputy leadership respectively and had been expected to endorse each other.

But Ms Rayner, the shadow education secretary, is being told that by championing Ms Long Bailey, the shadow business secretary, she would risk being dragged into the Corbynite battle over who should be the leftwinger to succeed him.

Neither Ms Rayner nor Ms Long Bailey has formally announced her intention to run but in setting out her pitch yesterday, Ms Long Bailey announced