The consortium’s review of the leaked documents found that Mr. Deng had acquired three additional offshore companies, well before Mr. Xi became China’s top leader and made a crackdown on corruption one of the centerpieces of his leadership.

The disclosures provide further insight into how China’s political elite has tapped into the global network of lawyers and wealth managers who, for a fee, can set up complex corporate structures that often have the effect of cloaking vast personal wealth.

It is not illegal for Chinese citizens to own companies offshore, and there are legitimate reasons for having one. Thousands of Chinese nationals have set up companies in offshore havens such as the British Virgin Islands and the Seychelles. Mossack Fonseca has more offices in China than in any other country, according to the company’s website.

Many of China’s most powerful families set up offshore companies during the administration of Hu Jintao, who preceded Mr. Xi as president and as leader of the Communist Party. Family members or close business associates of at least five of the nine men who served on the Politburo Standing Committee from 2007 through 2012 had links to offshore accounts, according to records reviewed by The New York Times.

Image President Xi Jinping in Beijing in 2012. The ties of Mr. Xi’s brother-in-law to offshore companies have been known for several years. Credit... Ed Jones/Agence France-Presse — Getty Images

It was during that period that Jia Liqing, the wife of Mr. Liu’s son, Liu Lefei, appears to have become the director and a shareholder of Ultra Time Investments, a company incorporated in the British Virgin Islands in 2009, according to the consortium's report. It is not clear what Ultra Time was used for, if anything. A Google search for the company’s name on Wednesday turned up only one result, a list of offshore “shelf companies” stating that Ultra Time had been incorporated on April 20, 2009.

Ms. Jia and her husband represent two of the most potent arms of the Chinese Communist Party. She is the daughter of China’s former minister of public security and chief prosecutor, Jia Chunwang, according to two people who have met the couple and who spoke on the condition of anonymity in order to preserve those relationships. Liu Lefei’s father oversees the country’s propaganda apparatus.