Australian prime minister John Howard’s conservative coalition government has invoked its federal powers to quash a law that would have been the country’s first to recognise gay marriages.

The Australian Capital Territory, which includes the national capital Canberra, last month voted to allow civil unions for same-sex couples, a move that ignited fresh debate on gay marriage in a way that has mirrored the US, where President George W. Bush is asking the Senate for a constitutional ban.