Labor's Justine Keay is on 52 per cent of the two-party preferred vote, despite polling 34.3 per cent of the primary vote.

The Liberals' Brett Whiteley is polling 40.7 per cent of the primary vote.

Labor is expected to benefit from preferences from the Greens' Jarrod Edwards, who holds 6.7 per cent of the primary vote, while controversial independent Craig Garland is polling 8.9 per cent.

More than two-thirds of voters said they would preference Labor above the Liberals.

The ReachTEL poll, commissioned by the Australian Forest Products Association, found 70 per cent of voters would be more likely to back a party or candidate "with policies that support north-west Tasmania's forest industries".

As well, 76.6 per cent of voters believed forest industries were important for the local economy and 65.3 per cent thought there should be a native forest timber industry for producing products such as decks and furniture.

AFPA chief Ross Hampton said the poll of more than 800 Braddon voters showed the by-election was on a knife-edge and the future of the forest industry would be a key issue.

He said his organisation had a six-point plan to grow the industry by driving new plantations, providing incentives for innovation and value-adding in timber and wood processing.

Prime Minister Malcolm Turnbull campaigned in Braddon on Friday, but is turning his attention to the Queensland seat of Longman on Saturday.

Braddon is one of five seats heading to the polls on July 28.

Australian Associated Press