The Singapore prime minister's brother, Lee Hsien Yang, said on Wednesday that he had joined an opposition party competing against his sibling at the upcoming July 10 election but that he was undecided on whether he would run as a candidate.

Lee Hsien Yang, the son of Singapore's modern-day founder, Lee Kuan Yew, has been embroiled in a bitter dispute with his brother over his late father's house. He told Reuters he had joined the new Progress Singapore Party (PSP).

Lee has criticised his brother Lee Hsien Loong's People's Action Party (PAP), which their father founded and which has governed the city-state since its independence in 1965.