Winnie Ho, the estranged sister of Macao gaming tycoon Stanley Ho, has launched a last-minute lawsuit to thwart the $500m Hong Kong initial public offering of his casino empire.

Ms Ho alleges that the Hong Kong stock exchange and the Securities and Futures Commission, the market regulator, failed in their legal duties when deciding to allow Sociedade de Jogos de Macau (SJM) to list in Hong Kong, the city's High Court heard yesterday.