Tory MPs have urged ministers to take a tougher approach towards China after the security services confirmed Beijing-backed hackers were responsible for a cyber-attack targeting the UK elections watchdog and a surveillance operation on British politicians. The Chinese ambassador will be summoned to explain his country’s actions, which resulted in Beijing allegedly accessing the personal details of about 40 million voters, held by the Electoral Commission. The National Cyber Security Centre, part of GCHQ, also found that four British parliamentarians who have been critical of Beijing were targeted in a separate attack. Two individuals and a front company linked to the cyber-espionage group APT31, which is associated with the Chinese ministry of state security, have been hit with sanctions by the UK as a result. Oliver Dowden, the deputy prime minister, told MPs that Beijing’s attempts to interfere with UK democracy and politics had not been successful, and that the government had bolstered its cyber-defence since the attacks. “We will not hesitate to take swift and robust actions wherever the Chinese government threatens the United Kingdom’s interests,” he said. “The UK judges that these actions demonstrate a clear and persistent pattern of behaviour that signals hostile intent from China.” The US, who also imposed a range of sanctions, and New Zealand said they supported the UK’s move. Merrick Garland, the US attorney general, said the case “serves as a reminder of the ends to which the Chinese government is willing to go to target and intimidate its critics, including launching malicious cyberoperations aimed at threatening the national security of the United States and our allies”. The disclosure marks a new low point in Beijing-London relations. Conservative MPs urged the government to take tougher action against Beijing and to add top Chinese officials to a register of hostile state actors. The parliamentarians whose email accounts were targeted in the attempted hack, which is believed to have involved sophisticated spear-phishing, were prominent critics of China. All four were members of the Inter-Parliamentary Alliance on China, an international network of legislators with a hawkish stance on Beijing. They included former Tory leader Iain Duncan Smith, former minister Tim Loughton, Scottish National party MP Stewart McDonald and cross-bench peer David Alton. At a press conference after a meeting with parliament’s head of security on Monday, the three MPs called for China to be formally labelled a threat to UK security. Duncan Smith said he and colleagues had been “subjected to harassment, impersonation and attempted hacking from China for some time” but MPs would not be “bullied into silence by Beijing”. He added: “We must now enter a new era of relations with China, dealing with the contemporary Chinese Communist party as it really is, not as we would wish it to be.” Robert Jenrick, the former immigration minister, said: “The government clearly is not holding China to account for their attack on our democracy. Taking three years to sanction two individuals and a small company is derisory. This feeble response will only embolden China to continue its aggression towards the UK.” Another Tory MP, Alicia Kearns, who chairs the foreign affairs committee, said: “This is sadly insufficient given the severity of the attack and the intent behind them. Two individuals and one firm is not deterrence. We need import controls and a comprehensive sanctions regime now.” The government was also criticised for being too slow to respond to the cyber-attacks, which took place between 2021 and 2022. Duncan Smith described the UK response as “like an elephant giving birth to a mouse” while McDonald accused ministers of “turning up at a gun fight with a wooden spoon”. Luke de Pulford, the executive director of the Inter-Parliamentary Alliance on China, said the government “was a little bit reluctant to say that China had actually done this”. David Cameron has raised the cyber-attacks on Britain’s democratic institutions directly with Wang Yi, the Chinese foreign minister. The foreign secretary addressed Tory MPs on the issue at a meeting of the backbench 1922 committee on Monday evening. The former prime minister, who was closely associated with the “golden era” of UK-China relations, has faced questions over his own role in a Beijing-backed development scheme in Sri Lanka. He faced criticism from Labour on Monday for meeting only Tory MPs. In a statement, Cameron said: “It is completely unacceptable that China state-affiliated organisations and individuals have targeted our democratic institutions and political processes. “While these attempts to interfere with UK democracy have not been successful, we will remain vigilant and resilient to the threats we face. We will always defend ourselves from those who seek to threaten the freedoms that underpin our values and democracy.” The two Chinese nationals were named as Zhao Guangzong and Ni Gaobin and the company as Wuhan Xiaoruizhi Science and Technology. Under the sanctions, their assets will be frozen and UK citizens and businesses barred from handling their funds or resources, while they will be subject to a travel ban to the UK. Pat McFadden, the shadow Cabinet Office minister, said he supported “efforts to counter attempts by China or any other state to interfere with or undermine the democratic process, or attempts to stop elected representatives going about their business, voicing their opinions or casting their votes without fear or favour.” Labour has warned China it will act against interference in UK democracy if it wins the next election, the Guardian has learned. Catherine West, the shadow Asia minister, travelled to Beijing last week for the first meeting between the opposition and the Chinese government since Keir Starmer became leader. China has rejected the claims. “The so-called cyber-attacks by China against the UK are completely fabricated and malicious slanders. We strongly oppose such accusations,” a spokesperson for the Chinese embassy in Britain said. “China has always firmly fought all forms of cyber-attacks according to law. China does not encourage, support or condone cyber-attacks.” A parliamentary researcher, Chris Cash, who worked for the China Research Group, an organisation co-founded by Tom Tugendhat, now the security minister, was arrested over allegations of spying last year.