North Otago also stay ahead as they continue their late season revival by upsetting South Canterbury 22-19 in the local derby, which was played in Dunedin.
Both teams scored three tries with Ben Palmer's penalty being the deciding points, with the loss dropping South Canterbury to third spot behind Poverty Bay.
Mid Canterbury were the latest side to put a whipping on the hapless East Coast, scoring 10 tries in a 67-12 destruction in Ruatoria.
Peni Manumanuniliwa grabbed a double while Murray Williams had a profitable day from a try, penalty and seven conversions.
In the other game, Wanganui's upcoming opponents Wairarapa-Bush emulated West Coast by getting a first win of the competition, coming from nine points down to beat Thames Valley 20-18 in Masterton.