Angela Rayner is expected to urge PM to let Greater Manchester mayor stand in Gorton and Denton byelection

Keir Starmer is facing mounting pressure not to block Andy Burnham from making a comeback to parliament, with Angela Rayner planning to urge No 10 to let him stand in a forthcoming byelection.

The prime minister’s allies have been trying to prevent Burnham’s return as a candidate in the Greater Manchester seat of Gorton and Denton, amid fears he could challenge the leadership.

However, a string of Labour MPs and the boss of Britain’s biggest union, Unison, warned on Friday that the party must ensure a democratic process and avoid a stitch-up.

Rayner, the former Labour deputy leader, is understood to be supportive of Burnham standing if he wants to, and is expected to argue he should be allowed to when she speaks at Labour’s north-west regional conference on Saturday.