According to Anbang, Caixin falsely claimed that Mr. Wu had married three times and “made a series of smears and slanders against our company’s legitimate business activities.” The marriage allegation appeared to refer to a report in Caixin in 2015.
Caixin responded to Anbang’s threat to sue with its own threat of litigation. On its website on Monday, Caixin said the suggestion that it took on Anbang out of vengefulness was “an attempt at framing with no basis in facts.”
“We strongly condemn the slander in the Anbang statement and reserve the right to take legal recourse,” Caixin said. A director of communications at Caixin, Ma Ling, declined to answer questions and referred to the online statement.
Caixin’s latest report on Anbang has been part of a burst of unwelcome attention for the company and Mr. Wu, which has thrown into doubt his business acumen and his reputation for political invulnerability.
“The level of detail that is provided in the article is, I think, relatively unique for any type of story of a Chinese company in Chinese media,” Christopher Balding, an associate professor at the Peking University HSBC Business School in the southern Chinese city of Shenzhen, said by telephone.
A lawsuit would pit a company that has recently appeared politically vulnerable against a magazine that has proved skilled at navigating censorship to report on corruption and financial shenanigans in China.
The controversy over Anbang has come while the Chinese Communist Party government under President Xi Jinping is seeking stability ahead of a leadership turnover later this year. But Mr. Xi also vowed in late April to rid China’s banks, insurers and other financial companies of excessive risk. Last month, Xiang Junbo, the chief regulator of Chinese insurers, including Anbang, was put under investigation by party anticorruption investigators.
The questions raised by the article, and by the possibility of a lawsuit, may test whether the desire for stability will outweigh the government’s vows to take on nettlesome financial issues.
“Anbang is definitely a little bit more extreme and more aggressive than other Chinese insurance companies,” Mr. Balding said. “But at the same time, if you look at the finances of the insurance industry at large, and at individual insurance companies, their revenue and building and things like that were exploding by just astounding rates in the past few years.”
Guo Wengui, a Chinese businessman who fled abroad, has added to the recent jitters in Beijing by publicizing allegations — many of them lurid and difficult to corroborate — of corruption reaching into the party elite. Mr. Guo has also clashed with Caixin.
Mr. Wu’s family and personal ties are at the heart of the growing questions about Anbang, which he co-founded in 2004.
He has been a member by marriage of China’s political and business aristocracy: He married a granddaughter of Deng Xiaoping, the Communist patriarch who oversaw China’s market reforms in the 1980s. Mr. Wu also came close to sealing a partnership with American political royalty through Mr. Kushner, the New York developer who is a son-in-law and adviser of Mr. Trump.
Anbang was in talks with Mr. Kushner’s family company to pay $400 million for a stake in a flagship skyscraper on Fifth Avenue in Manhattan. Anbang bought the Waldorf Astoria hotel, a popular venue on the New York social calendar, in 2014 as part of a spree of acquisitions.
But the deal with Mr. Kushner’s company foundered in March, in the wake of growing controversy about a presidential in-law doing business with a Chinese conglomerate with many ties to Beijing’s political elite. Mr. Kushner has also become an influential White House adviser to Mr. Trump, including on China policy.
Anbang’s international luster had already dulled after it withdrew an application last year to buy an Iowa insurer, Fidelity & Guaranty Life, and also shelved a $14 billion bid to buy Starwood Hotels and Resorts. Before those deals foundered, American investors and regulators raised doubts about Anbang’s opaque ownership and its financial strength.
Now Caixin has laid out similar doubts for its readers. The Chinese news media had already raised questions about Anbang’s spending spree, but Caixin stepped into more sensitive territory by examining the group’s ownership and accounts in painstaking detail.
In 18 months from October 2014, Caixin estimated, Anbang had spent $16 billion on overseas acquisitions. But Caixin also said Anbang’s successive injections of capital, which have helped finance these deals, appeared to often involve companies linked to Mr. Wu’s relatives and associates, raising the possibility that they were not real injections by outside investors.
Anbang appeared to have “used circular injections of funding to magnify its capital,” the report said.
The Caixin report said those doubts were reinforced by Anbang’s complicated ownership. Many of those companies registered under obscure addresses, with little capital registered in their names, and often they were formed in clusters shortly before they bought into Anbang — findings that echo the Times report. The names, addresses and other details of dozens of people registered as holding shares suggested that they were Mr. Wu’s relatives and associates.
Until recent days, Anbang was mostly silent about the reports on Mr. Wu and the group’s finances, including internet-born rumors that he had been held as part of a criminal investigation. No Chinese officials have said anything to suggest that Mr. Wu was detained or under investigation.
But since late last week the company has fought back. Anbang issued a statement on Friday that it had sufficient cash flows; it told a Chinese newspaper that rumors that Mr. Wu was in detention were false; and Mr. Wu gave an interview to another Chinese newspaper, The Beijing News, that also seemed intended to squash the rumors.
Mr. Wu said in the interview that Anbang was especially enthusiastic about Mr. Xi’s plan to expand Chinese investment and construction abroad in a much-promoted plan called “One Belt, One Road.” Now investors and political analysts will watch to see whether Mr. Xi’s government takes sides in the dispute between Anbang and Caixin.
“Hu Shuli and Caixin have done an amazing job carving out a space for honest and incisive reporting in China’s heavily censored media,” Victor Shih, a professor at the University of California, San Diego, who studies finance and politics in China, said by email. “Caixin will need all of its savvy to navigate the Anbang lawsuit though.”