Yorkshire failed to defend a 182 target as Lancashire pinched a Roses Vitality Blast six-wicket win at Emerald Headingley to dent the Vikings quarter-final hopes.
The White Rose were hurt by losing eight wickets for 51 in the last 8.1 overs of their own innings as they posted 181-9 having opted to bat.
David Willey starred with a blistering 80 off 43 balls with five leg-side sixes, while Tom Kohler-Cadmore hit 46.
But they slipped from 102-1 at halfway and later 130-1, with Australian James Faulkner striking three times in the last four balls of the innings.
In-form England Lions opener Alex Davies then flew out of the blocks with three sixes in a quick-fire 34, sharing 57 inside six overs for the first wicket with Karl Brown, who top-scored with 51 off 34.
Pinch-hitter Arron Lilley crashed a career best 47 off 20 balls with four fours and four sixes as the win was secured with 14 balls to spare.
This was Yorkshire’s fifth defeat in 11 North Group games, and Lancashire have overtaken them in the race for a top four finish. They have 13 points to Yorkshire’s 12 with three to play.
Lancashire were without captain Liam Livingstone and Jos Buttler from last month’s meeting at Emirates Old Trafford, which they also won.
But they were able to secure a first win in five games since winning that home fixture.
After Steven Croft and Faulkner conceded six from the first two overs of the match, Yorkshire really got going through Willey, who was ably supported by Kohler-Cadmore.
Kohler-Cadmore, who hit 46 off 33, was dropped twice in the deep but was happy to give Willey the strike as the Vikings reached halfway at 102-1.
After Kohler-Cadmore was dropped for the first time on nine off Faulkner in the fourth over, Willey hit two of three fours in the over and later reached 50 off 31 balls with his fourth leg-side six.
Willey and Kohler-Cadmore shared 129 in 11.4 overs for the second wicket to recover from 1-1 in the first over.
Lancashire’s fielding was sloppy, but they hit back well through Faulkner’s treble and two apiece for Zahir Khan and the impressive leg-spinner Matthew Parkinson.
Davies offered a difficult chance to Steve Patterson at mid-on on five before hitting Tim Bresnan for two sixes and a four in the fifth over to take Lancashire’s score to 57-0.
He fell in the next, however, when Patterson bowled him as he aimed a reverse scoop.
But Lilley built on the momentum with a swashbuckling display, included two sixes in one Azeem Rafiq over, as he bettered the previous career best 42 not out he scored against Yorkshire last month.
When he fell to Jordan Thompson courtesy of a brilliant diving catch at deep mid-wicket by Willey, Lancashire were 114-2 in the eleventh.
Brown reached 50 off 33 balls, but Yorkshire were left with too much to do to drag things back even though he was one of two wickets to fall (run out) in the 15th over as the score fell to 162-4.
Yorkshire are back in action tomorrow night (6.30pm) when they travel to Trent Bridge to tackle champions Nottinghamshire, who have an uphill task to qualify this year.
It is the first of two meetings with Notts in the last three games.