Keir Starmer has been put “on notice” by the leader of Britain’s biggest trade union, who said that its support should not be treated as a “blank cheque”. Sharon Graham, the general secretary of Unite, signalled a rift remained with the Labour leadership despite delegates voting to remain affiliated with the party. A debate was held at Unite’s rules conference in Brighton on whether the union should sever ties with Labour. Such a move could have seriously hampered Labour’s finances, as the union is the party’s biggest donor. It would have paved the way for allowing Unite to donate money to other parties or candidates – such as the independent MP Jeremy Corbyn, Starmer’s predecessor as Labour leader. Delegates “overwhelmingly” chose to retain Unite’s formal link with Labour, with Graham among those who spoke in favour. “This is the moment of maximum leverage for the union where we can hold Labour to account,” she said. “Now cannot be the time to walk away. We would be weakening our own arm. “It would be the worst time to leave the Labour party when they are in touching distance of power. If we leave we wouldn’t influence that power.” However, Graham had a warning for Starmer, whom she has frequently aimed terse comments at over his leadership. “Labour must be Labour and the union must push them into that position,” she said. “We must make them take different choices. We will not make the same mistakes of the past. There will be no blank cheques for Labour until we see tangible results.” In a statement on Twitter, the Unite union also said that Graham had put Starmer “on notice” to “deliver on jobs, pay and conditions if he wins power at the next election”. The motion pushing for a rule change that would have allowed Unite to give support to other “political candidates” was tabled by the north-east, Yorkshire and Humber regional industrial sector committee for health. But pushback came from the Unite executive council. A message to delegates urging them to support continued affiliation said: “Supporting other political parties or supporting candidates who stand against official Labour candidates would mean automatic expulsion under Labour party rules. “It is our position that this would not be in the interests of our union at this time – especially so close to a general election.” Unite, which has about 1.4 million members, has been a persistent thorn in the side of the Labour leadership under Graham since she was elected to the top job in August 2021. Most recently, she criticised as “beyond belief” the refusal of shadow chancellor, Rachel Reeves, to commit to endorsing the recommendations of the pay review bodies on public sector pay given the cost of living crisis. In the spring, Graham also criticised as “reckless” what she said was a lack of detail about Labour’s plans to ban new oil and gas drilling to reach net zero, voicing concerns about the impact on tens of thousands of workers. Greg Hands, the Conservative party chairperson, said the result of Monday’s vote was “a reminder who pulls the strings behind the Labour party – the trades unions”.