Keir Starmer’s shadow employment secretary was accused of sabotage on Monday night after he quit in protest at the Labour leadership in a move that colleagues said was designed to overshadow a £28bn green spending pledge. The shadow chancellor, Rachel Reeves, unveiled one of the party’s key policies of its annual conference earlier in the day, saying a Labour government would invest £244bn over eight years in tackling the climate crisis. But within hours Andy McDonald resigned over Labour’s failure to support a £15-an-hour minimum wage and said the party was “more divided than ever”. The Guardian understands Labour activists opposed to Starmer are intending to capitalise on the resignation with a protest to demand the living wage rise during his speech on Wednesday. McDonald had worked closely with the deputy leader, Angela Rayner, on the party’s offer on workers rights but it is understood she and Starmer were blindsided by the resignation. A senior Labour official said: “This is clearly a pathetic orchestrated attempt to undermine the changes happening in the party. We won’t be losing any sleep over this attempt at sabotaging Labour conference.” McDonald denied that the resignation was orchestrated or political, and told the BBC he had resigned as a point of principle. In his resignation letter, McDonald said his role had become untenable and 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.” He said he had been “instructed to go into a meeting and argue against a national minimum wage of £15 an hour and against statutory sick pay at the living wage. This is something I could not do.” McDonald launched a green paper on workers’ rights with Rayner last week, which included a £10 minimum wage proposal. A shadow cabinet source said: “If we are to take his argument at face value, it appears he’s resigned on the basis of a policy he agreed and announced at the weekend.” Relations between Starmer and McDonald had been on shaky ground. The Guardian understands the Labour leader intended to sack McDonald in the reshuffle in the spring but reversed the decision after a row over Rayner’s role, giving her the “future of work” brief to which McDonald contributed. In a short response on Monday, Starmer thanked McDonald and pointedly referred to his own work on employment rights. “Labour’s comprehensive new deal for working people shows the scale of our ambition and where our priorities lie,” he said. “My focus and that of the whole party is on winning the next general election so we can deliver for working people who need a Labour government.” Several shadow cabinet ministers expressed anger at links with the former shadow chancellor John McDonnell, whose ex-media adviser Andy Whittaker helped coordinate the announcement of McDonald’s departure. Concern had also been raised internally about an event at the Momentum fringe festival where McDonald had been due to speak with the former Labour leader Jeremy Corbyn, who currently has the Labour whip suspended. A shadow cabinet source compared McDonald’s departure disparagingly to the return of the former MP Louise Ellman, who quit the party over antisemitism in 2019. On Monday she said she had returned as she was “confident that under the leadership of Keir Starmer the party is once again led by a man of principle in whom the British people and Britain’s Jews can have trust”. Charlie Falconer, the shadow attorney general, suggested McDonald’s departure may have been deliberately timed to distract from “the message that Rachel Reeves is giving the country”. He told Sky News: “He leaves on a day when the party has chosen a particular direction … this conference made it clear what they wanted with the reception they gave Rachel Reeves this morning.” Steve Reed, the shadow communities secretary, said: “We all of us need to be disciplined enough to focus on the things that matter to the people of this country ... The party is rallying round Keir in a way I’ve never seen in a very, very long time.” Reeves was caught off guard in a fringe meeting as the departure was announced. However, key leftwing figures said the resignation was an indictment of the leadership. In the conference hall, members cheered as one heckler shouted “solidarity with Andy McDonald”. Len McCluskey, the former Unite general secretary, called McDonald “a really decent man” and said: “He makes the point that Keir was elected on a radical platform and yet he has abandoned that radical platform and the party is moving more and more away from it.” Mish Rahman, a Momentum member of the Labour NEC, said: “Labour has to be the party of working people not bosses. During the leadership election it seemed like Starmer understood this, but this resignation proves he does not.” Richard Burgon, the former shadow cabinet minister, said McDonald had “put up with an awful lot to drive through a superb programme of workers’ rights … To instruct him to drop his principles on wages and sick pay was a huge misjudgment of Andy and the movement.”