Rishi Sunak’s “spiteful” new anti-strike laws have created a “galvanising moment” for the UK’s trade union movement, the TUC general secretary has said. Speaking before a special congress of union leaders on Saturday about how to respond to the Strikes Act, Paul Nowak promised the TUC would throw its weight behind any worker hit by the new law. “We want to repeal this legislation, but in the meantime we’re absolutely clear that we’re going to defend any worker who exercises that right to strike. That’s our starting point,” he said. “This will be a galvanising moment for the whole trade union movement.” Passed in July in the wake of the biggest wave of public sector strikes for a generation, the act allows the government to set minimum service levels to be met on strike days. With more rail strikes expected in the coming weeks in the long-running dispute between the train drivers’ union Aslef and the Rail Delivery Group, the legislation could soon face its first practical test. The Tory chair of the transport select committee, Iain Stewart, said recently there was “a risk of minimum service levels worsening worker-employer relations” and that they could “end up making services less reliable”. Before a strike, employers will be expected to draw up lists of individuals they deem necessary for maintaining the minimum service levels. Those named in such “work notices” will not be allowed to strike and could be sacked if they do so. If unions fail to take “reasonable steps” to ensure the work notices are complied with, they could be sued for damages of up to £1m. The legislation was drawn up by the then business secretary, Grant Shapps, as strikes swept through schools, the NHS and the railways, in many cases forcing the government to offer enhanced pay deals. Nowak said of the new law: “I think it genuinely is a very spiteful response to the fact that we did have people taking industrial action this year, not because they were desperate to stand on picket lines but because they felt they couldn’t afford another year of real-terms pay cuts.” He suggested Sunak’s government would ultimately fail in trying to use strikes as a political dividing line. “There hasn’t been a huge public backlash against teachers or nurses or railway workers or anybody else for taking strike action,” he said. “I don’t think they’ve managed to construct a wedge between unions and the public.” Detailed regulations were passed in parliament this week specifying the minimum service levels for rail workers, border staff and the ambulance service, with others such as education expected to follow. Rail workers will be expected to ensure at least 40% of trains run, for example. Unions passed a motion on the Strikes Act at the TUC’s annual congress in Liverpool in September calling for “mass opposition to the minimum service levels laws, up to and including a strategy of non-compliance and non-cooperation to make them unworkable, including industrial action”. Nowak stopped short of suggesting unions deliberately flout the law, given the potentially huge financial damages. He said unions would not walk into “bear traps” set by the government. “We’re not going to leave legal hostages to fortune.” He said this weekend’s gathering would explore all other avenues, and he warned that unions could find themselves inadvertently on the wrong side of the legislation. The statutory code of practice accompanying the law says strike stewards should not try to prevent individuals mentioned in a work notice from crossing picket lines, for example, but unions have said they may not be able to identify every person involved. “We’ll be using the congress on Saturday to set out in detail, what will we do the first time a worker is sacked as a result of this legislation, the first time a union is sanctioned, what we’re going to do to win public support, what we’re going to do in terms of our legal strategies,” Nowak said. The TUC has already referred the legislation to the International Labour Organization, arguing that it undermines the right to strike. After details of the minimum service levels for the Border Force, railways and the ambulance service were published last month, the House of Commons joint committee on human rights wrote to the business secretary, Kemi Badenoch, expressing “serious concerns”, saying that some workers would in effect be prevented from ever striking. When ministers drew up plans for the legislation, a spokesperson said: “The government will always protect the ability to strike, but it must be balanced with the public’s right to life and livelihoods.” Labour has promised to repeal the legislation as part of a package of measures known as the “new deal for working people”, drawn up in collaboration with unions.