White brought up his half-century in the 13th over, but Parry struck again, and in similar fashion, when David Sales holed out to Saj Mahmood at long-on.
White picked up the pace, hitting Darren Powell for three sixes in four balls in the 17th over before an attempt to pull Mahmood ended in a skied top edge to Tom Smith at extra cover.
Smith bowled Wakely to reduce Northants to 145-4 at the end of the 18th over, but Andrew Hall and Elton Chigumbura hit 25 off the final two overs to ensure the hosts reached what looked to be a very competitive total.
Lancashire's reply began badly when Brooks, who bowled tightly in tandem with Vaas, took the edge of the bat as Moore drove hard.
Tom Smith clipped a low David Willey full toss straight to midwicket, and Croft's innings of 24 off 20 balls ended when he was well caught behind off an inside edge off Chigumbura.
Wakely's remarkable catch, leaping high to hold the ball and somehow stay inside the boundary rope, ensured there would be no recovery, though Gareth Cross and Mahmood hit 50 off the final 22 balls to reduce the winning margin.
BBC Radio Northampton's Geoff Doyle: "A much better performance from Northants with the bat and ball.
"Rob White has had a sticky patch with the bat recently and so his knock was much needed for team and individual.
"With the ball, Middlebrook and Brooks were the key bowlers taking wickets and keeping line and length tight for what was a very short boundary."
Northants captain Andrew Hall told BBC Radio Northampton:
"We've played exceptionally well in this game. Everything came together.
"We had a polished batting performance - for a change - and then we made a great start with the ball.
"After the 14th or 15th over the game was pretty much dead - which was great."
Stand-in Lancashire captain Mark Chilton told BBC Radio Lancashire: "We did a lot of good stuff but we probably did just did a bit too much bad stuff.
"I thought Crossy (Gareth Cross) did wonderfully well near the end to get us anywhere near but we could never get ahead of the run-rate.
"It would be good to get a win on Sunday going into that quarter-final and come off the back of a really strong performance."
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