Thailand's top court questioned on Tuesday the legality of Bangkok's support for a Cambodian bid to list a disputed Hindu temple as a World Heritage site, giving the opposition another weapon to attack the government.

The Constitutional Court ruled 8-1 that a communique approved by the cabinet in June backing Cambodia's bid to list the 900-year-old Preah Vihear temple had required the approval of parliament.

UNESCO, the U.N. agency for culture and education, voted on Monday to approve Cambodia's request to register the temple, which has been at the centre of a bitter 50-year dispute on the Thai-Cambodian border.