A new poll shows Labor's primary support falling to 29 points.
The Nielsen poll published in Fairfax papers on Monday shows Labor's primary support falling three points, while the Coalition is up three points at 47.
The two-party preferred numbers put Labor at 43%, with the Opposition on 57%.
The ABC reports the shift in voter sentiment is beyond the poll's margin of error and is most noticeable among male voters, where there has been a drop of 7% in support for Labor.
The Fairfax poll says that the Government's primary vote would rise to 40% if former prime minister Kevin Rudd took over the leadership from Prime Minister Julia Gillard, with the Coalition dropping to 42%.
It says the two party-preferred vote would be even on 50% for both parties if Mr Rudd was leading Labor.
The ABC reports there is a clear campaign within Labor to build momentum for Mr Rudd to return to the leadership, but it is not clear how, as he has repeatedly ruled out a challenge.
A federal election is due to be held on 14 September.