Speaking at the airport, he rounded on critics who believe that Mr Leung was treated harshly for breaking rules related to his business affairs. "If you have discovered that the Director of Immigration couldn't pass an integrity check but the government had swept it under the carpet and let him stay in office, you would have pilloried the government and rightly," he told reporters.
On Wednesday the government finally admitted that Mr Leung had been forced out, having agreed with him to tell the public that he was stepping down for personal reasons. However legislators believe that the government has still not come clean about the reasons for Mr Leung's departure and will summon the Chief Secretary, Anson Chan, for further questioning next week.
The legislator's disquiet is fuelled by a steady trickle of new allegations about Mr Leung and a growing number of unanswered questions.
A senior official in Ottawa told The Independent yesterday that special arrangements were made for Mr Leung to secure Canadian citizenship which circumvented normal immigration rules. Mr Leung has consistently stressed his good relations with officials from the incoming Chinese regime and it is unclear why he wanted a Canadian passport.
However in 1989, the year he became director, his wife and children emigrated to Canada where they bought a luxurious flat in Vancouver. In 1993 his daughter Sylvia was murdered with a crossbow. Police are investigating a link with Chinese triad gangs. The Leung family and Sylvia Leung's boyfriend were the victims of at least five arson attacks before the murder.
All family members are now back in Hong Kong where they have become embroiled in the financial controversy which the government has cited as the reason for Mr Leung's forced resignation. Both Mr Leung's son Hugo and his wife, Kitty, are directors of companies alongside Mr Leung. He failed to declare his interest in them when asked to do so by his superiors.
One of the companies, the New China Hong Kong Advertising Company, is linked to the New China Hong Kong Group, an investment company founded by Tsui Tsin-tong with the backing of the Chinese authorities. Mr Tsui, a benefactor of the British Museum, is known to have been an arms trader.
It appears that while head of the immigration department, responsible for sensitive dealings with Chinese officials, Mr Leung was trying to establish a business in China with one of the Hong Kong businessmen closest to China's government.
Another of Mr Leung's undisclosed businesses, Dragon House Investments, was linked to Lau Wong-fat, one of the legislators with the best relations with Peking. Mr Lau is an influential figure in Hong Kong's rural areas where he has extensive property holdings.
Most of Hong Kong's Chinese language newspapers yesterday suggested that the financial irregularities surrounding Mr Leung were insufficient to justify his dismissal. Mr Patten said he was amazed by those suggestions.