A 20 runs win put them equal top with Essex on 36 points after 12 matches, and it's all set up for a big finish to the 40 overs competition over the next month.
Neil Fairbrother, whose unbeaten 82 played a major part in Lancashire's triumph said: ``We are playing well, with a lot of confidence and we're in with a shout now.''
Returning after an ankle injury for his first game in three weeks, Fairbrother hauled Lancashire to a useful 183-7 on a tricky pitch. Then the last eight Leicester wickets tumbled for 38 as they were shot out for 163 and their coach Jack Birkenshaw admitted: ``Lancashire came back at us with a very disciplined bowling performance and we crumbled under the pressure.''
Leicester, at 130-2 with 10 overs left and Ben Smith batting magnificently, were odds-on favourites, but Wasim Akram sent back the danger man - and then made the decisive attacking switch by replacing himself with Ian Austin.
The country's most dependable one-day bowler produced a wicket maiden in the 35th over to rock Leicester back on their heels, and Peter Martin caused mayhem a few minutes later with three wickets in four balls.
Austin, finishing with 7.4-2-8-3, and Wasim wrapped it up as Lancashire stayed on course for the treble.
The rain-hampered championship game against Leicestershire was finally washed out today without a ball bowled.
England selected the same team for Thursday's final Test against South Africa.