The UK’s main union body has reported the government to the UN’s labour standards organisation for alleged attacks on workers’ right to strike. The Trades Union Congress (TUC) said ministers had taken several steps to infringe the right to strike, including a new law that allows companies to use agency workers to break strikes and a proposal for a minimum service level on transport and other “critical” sectors. The submission to the International Labour Organization, an agency of the United Nations that sets standards for workers around the world, follows a pledge from Liz Truss – who will be appointed prime minister after being named winner of the Conservative leadership race on Monday – pledged to crack down on unions within the first 30 days in office. Frances O’Grady, the TUC general secretary, said the government was seeking to limit workers’ ability to bargain for better wages just when inflationary pressures are reaching their peak. “The right to strike is a fundamental freedom,” she said. “But the Conservative government is attacking it at every opportunity. Threatening this right tilts the balance of power too far towards employers, and breaches the legal obligations ministers signed up to in government.” Relations between unions and the government have almost completely broken down in recent months, as low unemployment and rapidly rising prices have prompted an increased number of industrial disputes. That has spilled over into a wave of strike action for higher pay and better conditions across sectors ranging from rail and port workers to Royal Mail employees and even barristers. The TUC’s 31-page report, seen by the Guardian, detailed a series of law changes and proposals that it said would make it harder to strike. Those changes would impinge on rights of freedom of association and collective bargaining that should be guaranteed by ILO conventions ratified by the UK, the union body argued. It wrote: “The TUC is extremely concerned that these plans would severely impinge on unions’ rights […] in particular by making it extremely difficult to take effective industrial action.” If it decides the complaint is valid, the ILO has the power to censure the UK as a signatory to its conventions in reports. That could be embarrassing for the government, which regularly comments on rights in other countries. However, the ILO does not have the power to intervene directly in British lawmaking. The government has already introduced some laws this year that aim to limit the influence of unions. In July MPs voted through a law to allow companies to employ agency workers to replace striking workers, despite the objections of the Recruitment and Employment Confederation, a lobby group for businesses in the sector. Kwasi Kwarteng, who is tipped to be Truss’s chancellor, has previously said the changes to “burdensome, 1970s-style restrictions” are necessary to curb “militant trade union action”. Truss has threatened to impose legal minimum levels of service in critical national infrastructure. That could severely limit the ability of teachers, postal workers and the energy sector to take strike action, as well as transport workers who have staged several strikes across the country this summer. The prime minister to be sought during the Conservative leadership campaign to portray herself as a political heir to Margaret Thatcher, who fought against unions in the 1980s. In July, Truss said: “I will do everything in my power to make sure that militant action from trade unions can no longer cripple the vital services that hard-working people rely on.” Other changes mooted by the current transport secretary, Grant Shapps, would impose more detailed technical requirements before unions can take industrial action. They include banning strikes by different unions in the same workplace, limiting the number of pickets at critical infrastructure, requiring a 60-day “cooling off period” between strikes, and increasing minimum notice periods for strike action. Shapps also said the government would seek to “outlaw intimidatory language”, without detailing how that would work.