Prince Norodom Ranariddh, 74, was in a convoy along with senior members of his Funcinpec party heading toward Sihanoukville in southwest Cambodia when a taxi travelling in the opposite direction slammed into his SUV, said a senior party member in the group.
Ranariddh's wife, Ouk Phalla, who died in hospital after the crash, was also standing as a candidate in Cambodia's general election next month.
Ranariddh suffered head injuries and was transferred to Phnom Penh for urgent treatment, Sihanoukville police chief Chuon Narin said.
Ranariddh was Cambodia's co-prime minister for four years in an uneasy power-sharing arrangement with current Prime Minister Hun Sen after his party won a United Nations-organised election in 1993.
His party's popularity was largely due to its royalist credentials, although Ranariddh's personal relations with his popular father, late King Norodom Sihanouk, were often strained.
He was ousted in July 1997 and fled abroad when long-simmering tensions between him and Hun Sen exploded into two days of bitter fighting in Phnom Penh between his forces and those loyal to Hun Sen.
Ranariddh was allowed to return to contest elections the following year but failed to repeat his success at the ballot.
He slid into political irrelevancy, as Funcinpec became co-opted by Hun Sen, a much savvier and tougher politician than Ranariddh.
Ouk Phalla, a classical Cambodian dancer reported to be descended from a separate royal family branch, was Ranariddh's second wife./-
