A shadow cabinet minister has quit Keir Starmer’s top team, citing the leadership’s failure to support a GBP15-an-hour minimum wage and saying Labour is “more divided than ever”.

Andy McDonald, the shadow secretary of state for employment rights, worked closely with Starmer’s deputy, Angela Rayner, and was regarded by trades unions as a guarantor of their influence in policymaking.

In his resignation letter, which came in the middle of the Labour conference and as the party sought to switch the focus from internecine wrangling over rule changes to policy, McDonald said his role had “become untenable”.

“When you became leader, I accepted the role because I wanted to fight for the working people of this country. It has become clear to me that I cannot do this as a member of the shadow cabinet,” he told Starmer.

“Yesterday, your office instructed me to go into a meeting and argue against a national minimum wage of GBP15 an hour, and against statutory sick pay at the living wage. This is something I could not do.”

He added: “After 18 months of your leadership, our movement is more divided than ever and the pledges you made to the membership are not being honoured.”

McDonald said he looked forward to being “free to fight for working people”.