Australia's Greens Party launched its campaign for the August 21 election Sunday, pledging support for legalising gay marriage and euthanasia, and to fight for the environment. The country's third-largest party hopes to win an additional Senate seat in the election, which would give it a hold on the balance of power and a role as a policy arbiter between Labor and the Liberals, the two major parties. Greens leader Bob Brown unveiled a policy platform that included support for gay marriage and euthanasia for terminally ill patients as well as a pledge to do more to fight carbon emissions and to protect marine life. He accused Prime Minister Julia Gillard's Labor Party and the conservative Liberal Party of a 'failure of vision' in leading Australia, saying the Greens offered a 'responsible review' of policy 'with a dividend for the people.' 'If you're going to move forward, you have to say where you're going,' he said, in a comment on Gillard's 'Moving Forward' election slogan. He reserved his harshest criticism for the opposition Liberal party, saying that if it took control of the lower house of parliament or picked up another seat in the Senate it would be bad for the country. 'The polls yesterday indicate there may be an (opposition leader Tony) Abbott government. If that is so, it is quite possible that they will pick up one more seat in the Senate,' Brown said. Referring to the Greens' policy on euthanasia, he said Australians should have the right to take their own life and die with dignity. 'The great majority... 80 percent of all opinion polls... show Australians want the right, their right in dying to make their choice.' He also appealed to Gillard to support gay marriage, pointing to Argentina, which last week made the practice legal. 'If South Africa can do it, if Argentina can do it, if Catholic Spain can get rid of that discrimination, why not you, Julia Gillard?' Popular support for the Greens, the country's third party behind Labor and the Liberal Party, rose to a record 16 percent in an opinion poll published in June and was at 12 percent in a Nielsen poll on Saturday. The party has five senators in the 76-seat Senate, where Labor has 32 and the Liberal-National coalition 37 and independent parties two. 