Senior shadow ministers have privately expressed doubt that Labour’s position on strikes is sustainable, after Keir Starmer sacked the frontbencher Sam Tarry for doing broadcast interviews from a rail strike picket line. The Guardian understands Tarry was told he was sacked as shadow minister for buses and local transport for saying that it was “not acceptable to offer below inflation pay rises” because it would be a real-terms pay cut for workers. Tarry was told Labour’s position was that it was for ministers and unions to negotiate terms. That dispute is likely to cause significant alarm from trade unions about Labour’s position, including those affiliated to the party. Frontbenchers told the Guardian they could be put in untenable positions with multiple industrial actions planned by unions in the coming months – including by rail workers, postal workers, NHS staff and teachers. “There are a lot of people saying, I don’t know if I can stay on the frontbench,” one senior source said. But there is also significant anger from the leader’s office that Tarry conducted a media round without any prior warning, and multiple sources suggested he had been goading Starmer to sack him in order to help him fight a difficult deselection battle. “Sam Tarry did a full media round without his boss Lou Haigh [the shadow transport secretary] or the leader’s office knowing in advance,” a Labour source said. “This represents a total breakdown of discipline and put the leadership in a position where it was impossible to do anything else.” Starmer has told shadow ministers not to join picket lines, stressing that Labour is a party seeking to govern that should aim to solve disputes. Several shadow ministers who joined picket lines during the last strike did not lose their jobs, despite the warning. Advertisement A Labour party spokesperson said: “The Labour party will always stand up for working people fighting for better pay, terms and conditions at work. “This isn’t about appearing on a picket line. Members of the frontbench sign up to collective responsibility. That includes media appearances being approved and speaking to agreed frontbench positions. “As a government in waiting, any breach of collective responsibility is taken extremely seriously and for these reasons Sam Tarry has been removed from the frontbench.” Tarry, a former officer of the Transport Salaried Staffs’ Association (TSSA) union who helped run Jeremy Corbyn’s leadership campaign, has not previously joined picket lines as a shadow minister, though he had tweeted a picture of himself alongside workers on an earlier strike day. The TSSA general secretary, Manuel Cortes, said he was ashamed of the party. “Whatever excuses the Labour party makes about the reasons for Sam being sacked, the reality is that Sam has shown solidarity with his class and we applaud him for that,” he said. “If they think can win the next general election while pushing away 7 million trade union members, they are deluded.” The Unite general secretary, Sharon Graham, called the sacking “another insult to the trade union movement. Quite frankly, it would be laughable if it were not so serious. “At a time when people are facing a cost of living crisis, and on the day when the Conservative government has launched a new wave of attacks on the rights of working people, the Labour party has opted to continue to indulge in old factional wars.” Tarry, who is in a relationship with the Labour deputy leader, Angela Rayner, said in a statement he did not regret his actions. “As a Labour politician, I am proud to stand with these striking rail workers on the picket line in the face of relentless attacks by this Tory government,” he said. “It has been a privilege to serve on Labour’s frontbench for the past two years and to have had the opportunity to speak up for hard-pressed workers who deserve so much better than the treatment they’ve received from this corrupt and out-of-touch government.” Ruth Jones, a shadow environment minister, has also posted pictures supporting the latest strike, though not directly from picket lines. Shadow ministers including Alex Sobel and the Labour whip Navendu Mishra were spoken to by whips for joining pickets at the last strike but did not lose their jobs. Advertisement One shadow cabinet source said they believed Starmer’s position on picket lines would become unsustainable as the number of disputes intensified. “There will be other frontbenchers who will want to support striking workers in their constituencies,” they said. Another Labour source said: “Postal strikes will be a nightmare because it’s potentially hundreds of people in your constituencies. This would be supporting very moderate unions affiliated to the party. And MPs depend on support from unions.” However, senior Labour sources said they were sceptical of Tarry’s motives and linked it to his re-selection battle in Ilford South. Wards in Tarry’s constituency voted unanimously for a full reselection – meaning he is likely to lose the seat. They suggested Tarry was in effect daring Starmer to sack him. One called it “a pathetic, cynical stunt to get sacked”, and said: “He didn’t go to the first picket but has turned up now. So what has changed?” Tarry said after the interviews that he remained on the side of the striking rail workers. He has previously written to Labour’s general secretary, David Evans, suggesting he had seen evidence of voting irregularity in his selection battle. Tarry won selection in the east London seat in 2019 after the local council leader, Jas Athwal, was suspended from the party in the run-up to the vote over allegations of inappropriate behaviour. Athwal, an ally of the neighbouring MP Wes Streeting, was subsequently cleared in an internal investigation.