Aus Federal Labor is facing a historic defeat according to new poll ahead of the Super Saturday by-elections.

Federal Opposition Leader Bill Shorten speaks at the launch of the Labor campaign for the seat of Longman at the Caboolture RSL Source: AAP

Federal Labor is facing a historic defeat in the Queensland seat of Longman, and could also lose the Tasmanian seat of Braddon, according to new polling ahead of the Super Saturday by-elections.

YouGov Galaxy polling published by NewsCorp shows the opposition trailing 49 to 51 per cent in Longman, which was won by Labor's Susan Lamb at the last election.

In Braddon, support was 50-50 on a two party preferred basis, with the Liberals' Brett Whiteley on the verge of winning back the seat he lost to Labor's Justine Keay  in 2016.

Should Prime Minister Malcolm Turnbull snatch either seat in the July 28 votes, it would be the first time a government has won a seat from the opposition at a by-election in 100 years.