The stock market flotation of Ant Group, planned to be the biggest share offering in history, has been dramatically suspended just two days before dealings were due to begin in Shanghai and Hong Kong. The move came a day after the financial tech company’s top executives including its founder, Chinese billionaire Jack Ma, were summoned to speak to regulators. Details of the discussions were not published but a statement from the Shanghai stock exchange said Ant Group reported “changes to the financial technology regulatory environment and other major issues” in its meeting. “This material event may cause your company to fail to meet the issuance and listing conditions or information disclosure requirements,” the stock market operator said in its statement to Ant. As a result it suspended the planned listing, prompting Ant to put the Hong Kong leg on hold as well. China’s central bank issued new draft rules for online micro-lending on Monday that raised the amount of cash borrowers were required to hold. Ant Group owns Alipay, one of the dominant payment companies in China, alongside other subsidiaries including lenders to consumers and small businesses, a credit-scoring company and a healthcare payment products provider. The suspension threatens to derail the biggest ever corporate fundraising just days after it attracted huge interest from institutional and retail investors across the world, with bids worth $3tn chasing $34bn (£22bn) worth of shares. According to the original timetable Ant had been scheduled to list on the Hong Kong and Shanghai exchanges on Thursday. The listing had been expected to confirm Ant’s status as one of the world’s biggest companies by valuation, with an expected market value of more than $310bn before shares started trading. That would mean it would rival the valuation of JP Morgan, the world’s most systemically important bank. As well as its significance for the company, the move was seen as a symbolic moment in China’s development as a financial centre, with one of the world’s biggest companies eschewing a New York listing, unlike its former parent company, Alibaba, the online retail company founded by Ma. Meziane Lasfer, a professor of finance at City, University of London, said the lateness of the decision to suspend the listing could be harmful to China’s efforts to grow its financial sector. However, he said the greater risk to China’s reputation would be allowing the flotation to go ahead if it had truly identified regulatory problems. A predecessor to Ant Group was spun out of Alibaba in 2011 but the latter retained a significant stake. New York-listed shares in Alibaba lost 6% on Tuesday. His stakes in Alibaba and Ant Group have made Ma, a former English teacher, China’s richest man. Ant’s Alipay, launched in 2004, has more than 1 billion users in China, and its Yu’e Bao money market fund is one of the biggest in the world. However, Chinese firms are also subject to regulation by the Communist party, which might be more cautious if it foresaw issues around a stock market float of Ant’s size, analysts said. Ma, who remains the public face of the company despite stepping back from day-to-day management, and the Ant Group executives, met China’s central bank and three regulators after the speech he made late last month criticising the Chinese banking system. Ma also questioned whether international financial regulations were suitable for China, according to reports from a public financial forum held in Shanghai. Ant said it sincerely apologised to investors for any inconvenience and would keep in touch with the Shanghai stock exchange and the relevant regulators.