Australia's Prime minister Julia Gillard has called a snap leadership ballot after being challenged by a senior cabinet minister to end the speculation that has destabilised the ruling Labor party. At the start of question time in Canberra, Ms Gillard said there would be a vote on the leadership and deputy leadership of the Labor party at 4.30pm on Thursday. http://link.ft.com/r/0QSDPP/CW9A2R/RN7YTC/PFIR0D/XBXCWI/XL/h?a1=2013&a2=3&a3=20