The estranged sister of Macao gaming tycoon Stanley Ho launched a last-minute lawsuit to thwart the $500 million Hong Kong initial public offering of his casino empire, The Financial Times reported.

Winnie Ho claims that the Hong Kong stock exchange and the Securities and Futures Commission, the market regulator, failed in their legal responsibilities by deciding to allow Sociedade de Jogos de Macau (SJM) to list in Hong Kong, the city’s High Court heard Tuesday.

The judicial review application with SJM’s trading debut, scheduled for Thursday, is the latest twist in Ho’s long-running battle with her brother, the newspaper reported. She has reportedly launched more than 30 lawsuits in Macao and Hong Kong.

It is also the final obstacle on SJM’s road toward a listing.

The company, whose 40-year monopoly expired in 2002, is fighting for market share in the world’s biggest gaming market. It initially sought to raise $1 billion in January but was delayed after the market regulator sought clarifications over concerns raised by Winnie Ho. When Stanley Ho revived SJM’s listing plans last month, the offering had to be trimmed to $494 million, partly because of poor market conditions.

The lawsuit focuses on shareholdings in SJM’s parent, Sociedade de Turismo e Diversões de Macau, whose share registry has been lost. According to SJM’s prospectus, Winnie Ho holds a 7.3 percent stake in STDM while Stanley Ho, as the largest shareholder, controls more than 30 percent.

One of Winnie Ho’s arguments is that Hong Kong investors were not adequately warned of the risks arising from the confusion over, and legal challenges to, STDM’s shareholding structure.

Justice Anselmo Reyes was to decide on Wednesday whether to grant an injunction halting SJM’s listing.