Japan’s prime minister, Fumio Kishida, has announced that his ruling party will cut ties with the Unification church after a widening scandal caused by the assassination of the party’s former leader Shinzo Abe last month. Kishida also apologised for causing the loss of public trust in politics. Cozy ties between members of Kishida’s governing Liberal Democratic party, many of them belonging to Abe’s faction, and the South Korean-born church have surfaced since Abe was shot to death while giving a campaign speech in July. The suspect, Tetsuya Yamagami, who was arrested at the scene, allegedly told police he killed Abe because of his apparent link to the church. In a letter and social media posts believed to be his, Yamagami said he believed his mother’s large donations to the church had ruined his life. Some Japanese have expressed understanding, even sympathy, as details of the man’s life emerged, creating deep implications for the political party that has governed Japan virtually uninterrupted since the second world war. While religious groups must abide by law, “politicians are strictly required to be careful about groups with social problems”, Kishida said. Members of his cabinet and other key posts have agreed to review their past links and cut ties with the church. “As president of the LDP, I honestly express my apology,” Kishida said, apologising for causing the public’s doubts and concerns over the continuing revelations in media reports about the party’s extensive ties to the church. The Unification church, which was founded in South Korea in 1954 and came to Japan a decade later, has built close ties with a host of conservative lawmakers over their shared interests of opposing communism. Abe’s grandfather and former prime minister Nobusuke Kishi was a key figure who helped found the church’s political unit in Tokyo in 1968. Since the 1980s, the church has faced accusations of problematic recruiting, selling religious items and receiving donations, which often led to financial strains on followers’ families and, according to experts, the mental health of adherents’ children. The issues has led to the governing party’s decision to cut ties with the church. Abe sent a video message last year to the Universal Peace Federation, an international group affiliated with the church, which experts say may have motivated the suspect in Abe’s shooting. Abe had praised the federation’s cofounder Hak Ja Han Moon, who is also head of the church, for her efforts in promoting traditional family values. Experts and cult watchers also say that the church has promoted its key agendas such as opposition to women’s advancement and same-sex marriage to influence policy. Kishida shuffled his cabinet earlier in August to purge seven ministers linked to the church, among them Abe’s younger brother, Nobuo Kishi, who acknowledged that church followers volunteered in his election campaign. Dozens of LDP members have since come forward with their ties to the church and related organisations. Kishida said he has instructed the LDP secretary general, Toshimitsu Motegi, to survey the party over any other members’ ties to the church. Kishida apologised for the loss of public trust because of the scandal and his lack of explanation for organising a state funeral for Abe, one of the most divisive leaders in Japan’s postwar history. The state funeral, scheduled for 27 September, has split public opinion. Kishida’s cabinet last week allocated at least a 250m yen (£1.5m) budget to invite about 6,000 guests for the funeral at the Budokan arena in Tokyo. Kishida insisted that Abe deserved a state funeral because of his achievement in raising Japan’s global profile as its longest-serving postwar leader. He said Japan must respond with courtesy to the “outpouring of condolences” from foreign leaders and legislations. Hundreds of people gathered outside the parliament area later on Wednesday to protest plans for the state funeral. Holding signs and banners with messages “No to state funeral”, “Don’t force us to mourn”, and “Abe politics destroys Japan”, the participants chanted slogans and raised their arms.