Bay of Plenty's fears of dropping down to the Championship became a stark reality after losing to Tasman 17-3 at Trafalgar Park in Nelson on Thursday.
In a dull ITM Cup encounter, all the points were scored in the first half with Tasman running in two unanswered tries through full-back Tom Marshall and hooker Quentin MacDonald.
The result leaves Tasman in third place and close to sealing a semi-final berth after breaking a three-match losing streak, while Bay of Plenty remain in a battle to avoid relegation with just one game remaining against defending champions Canterbury.
The last-placed team in the Premiership are automatically relegated to the Championship.
Tries: Marshall, MacDonald
Cons: Marshall 2
Tasman: 15 Tom Marshall, 14 James Lowe, 13 Kieron Fonotia, 12 Andrew Goodman 11 Robbie Malneek, 10 Hayden Cripps, 9 Jeremy Su'a, , 8 Jordan Taufua, 7 Shane Christie, 6 Tevita Kolomatangi, 5 Joe Wheeler, 4. Filipo Levi, 3 Sam Prattley, 2 Quentin MacDonald, 1 Tim Perry
Replacements: 16 Francis Smith, 17 Reuben Northover, 18 Riki Hoeata, 19 Gary Redmond, 20 Steve Alfeld, 21 Peter Betham, 22 Sione Holani.
Bay of Plenty: 15 Nick McCashin, 14 Lelia Masaga, 13 Kenny Lynn , 12 Mafi Kefu, 11 Lance Macdonald, 10 Chris Noakes, 9 Lewis Hancock, 8 Carl Axtens, 7 Tanerau Latimer (c), 6 Jesse Acton, 5 Leon Power, 4 Dan Goodwin, 3 Josh Hohneck, 2 John Pareanga, 1 Greg Pleasants-Tate.
Replacements: 16 Nathan Harris, 17 Mike Kainga, 18 Keepa Mewett, 19 Matt Clutterbuck, 20 Jamie Nutbrown, 21 Simon Rolleston, 22 Jack Wilson.
Referee: Richard Kelly