Rishi Sunak’s new anti-strike legislation to enforce “minimum service levels” in key public sectors including the NHS and schools has drawn a furious reaction from unions as the prime minister scrambles to get a grip on industrial disputes. The law, which the government plans to introduce in the coming weeks, will allow bosses in health, education, fire, ambulance, rail and nuclear commissioning to sue unions and sack employees if minimum levels are not met. However, government sources said that plans in the original bill, drawn up by the former business secretary Jacob Rees-Mogg – for tougher thresholds for industrial action to take place – would be dropped amid concerns over possible legal action. Keir Starmer said he would repeal the anti-trade union legislation if Labour formed the next government, setting out clear dividing lines with the Conservatives on workers’ rights in the run-up to the next general election. Sharon Graham, the general secretary of the Unite union, said: “Yet again, Rishi Sunak abdicates his responsibility as a leader. Whatever the latest scheme the government comes up with to attack us, unions will continue to defend workers.” Under the plans, first proposed by Liz Truss’s government, minimum service levels will be set for fire, ambulance and rail services, with the government consulting on the adequate level of coverage for these sectors, to address concerns that disruption to blue-light services puts lives at risk. However, it will also reserve the power to impose minimum service levels in the other three public services – health, education, nuclear – although ministers expect to reach voluntary agreements in these areas and say they would only impose the anti-strike law if this were not possible. Government sources confirmed that union members who were told by their employers to work under the minimum service requirement but refused to do so could lose their jobs. The new law will also back employers bringing an injunction to prevent strikes or seeking damages afterwards if they go ahead. The Guardian has learned that even the government has admitted its approach of using minimum service levels to curb strikes could backfire. In an impact assessment published last year, the transport department said the move could push unions into striking more frequently as a way to put pressure on employers. The same document also warned that it could lead to workers taking more non-strike industrial action, such as refusing to work overtime, which could still cripple certain industries. Ministers claim the plans are about ensuring public safety, in the case of the health service, rather than attacking the unions. However, nurses came to their own national agreement about providing a minimum level of service during recent strikes. The ambulance service did not, meaning some patients suffering a heart attack or a stroke did not know there was help on the way. The business secretary, Grant Shapps, who has previously taken a hardline position towards unions, said: “As well as protecting the freedom to strike, the government must also protect life and livelihoods. “While we hope that voluntary agreements can continue to be made in most cases, introducing minimum safety levels – the minimum levels of service we expect to be provided – will restore the balance between those seeking to strike and protecting the public from disproportionate disruption.” With the country still facing further strikes this winter, which the new law would come in too late to prevent, ministers are also urging unions to cancel planned industrial action, suggesting that if they do so then pay rises could be on the table next year. Ministers invited union leaders to hold talks on next year’s pay review in an attempt to resolve current disputes “constructively through dialogue”. Sunak has already ruled out pay demands for this year despite millions of workers struggling with the cost of living. After a new year speech in east London, Starmer said: “I don’t think this legislation is going to work. I’m pretty sure they’d had an assessment that tells them that it is likely to make a bad situation worse. “We will look at what they bring forward but if it’s further restrictions then we would repeal it. The reason for that is that I do not think legislation is the way you bring an end to a dispute.” Unison’s head of health, Sara Gorton, said: “The public and health staff would welcome minimum staffing levels in the NHS every day of the week. That way, people wouldn’t be lying in agony on A&E floors or dying in the backs of ambulances. “But limiting legal staffing levels to strike days and threatening to sack or fine health workers when there are record vacancies in the NHS show proper patient care isn’t what ministers want. “The government is picking ill-advised fights with NHS employees and their unions to mask years of dismal failure to tackle pay and staffing.” Gary Smith, the general secretary of the GMB, said: “A government that has presided over 13 years of failure in our public services is now seeking to scapegoat the NHS staff and ambulance workers who do so much to care for the people of our country. “The NHS can only function with the goodwill of its incredible staff, and attacking their fundamental right to take action will alienate them even further and do nothing to help patients and the public.” The general secretary of the Royal College of Nursing, Pat Cullen, said curtailing workers’ freedom to participate in lawful industrial action was “always undemocratic” and the union would look closely at the government’s plans next week. She said: “Safe staffing levels that are set in law are what we want to see year-round, not just in these extreme circumstances. “We’ve long campaigned for governments to be accountable for safe and effective staffing levels in the NHS and social care to prevent one nurse being left with 15, 20 or even 25 sick patients. Legislation exists in other parts of the UK and England is lagging behind. “The evidence is unequivocal: safe staffing saves lives and having the right number of registered nurses on duty has a direct impact on the safety and quality of patient care. Today’s highly unsafe situation is what is driving our members to say ‘enough is enough’.”