UPDATE: Facilitator Joe Hildebrand kicked off the final leader's debate of the 2016 by calling for a slogan-free zone.
The debate, hosted via social media rather than television, gave the first answer to Prime Minister Malcolm Turnbull.
Both he and Mr Shorten were called on to address the lack of trust voters now give to the leaders of each major party after a series of changes in leadership.
The debate audience has only 30 people in the audience, chosen from marginal seats.
EARLIER: PRIME Minister Malcolm Turnbull and his opposite number Bill Shorten will go head-to-head in a live, online debate hosted on social media tonight.
The leaders have not met since the first leaders' debate on Sky News three weeks ago, with Mr Turnbull rejecting an invitation to a second Sky debate last week.
Mr Turnbull had said he wanted the debate to be more open to people to contribute questions, preferably through social media, and declined the second debate, with Mr Shorten having the debate to himself.
The pair of political opponents will face online questions through Facebook, and hosted bynews.com.au, from 6pm tonight.
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