Champions Bardsey lost a vital match against third from bottom Roundhay by 58 games to 50 - a defeat which could cost them the First Division title.
Horsforth are now favourites to take the title.
It was a weakened Bardsey side that went down to Roundhay, lacking Adrian Lobley, Syvila Billington, Tim Dickinson and Dot Mackintosh.
But Bardsey's first pairing of Tawona Moyo and Rachel Jackman did not let them down, winning all three rubbers.
The combination of Mike Walker and Becky Brown secured one victory while Julian Howes and Alex McNaughton failed to win a match.
Whitkirk have finished on 36 points with nine wins from 12 matches. Horsforth, with two matches in hand, are already on 36 points. Third placed Bardsey are on 28 points, also with two fixtures in hand on the top side. But in reality Horsforth are within touching distance of the trophy.
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