County Championship division two leaders Worcester crumbled in the face of England Test bowlers present and past Anderson and Graham Onions having been put in.
South African Parnell’s 63 was at the heart of their recovery to 172 before returning 3-19 from 10.4 overs as Lancashire closed on 88-5 from 36.4.
Anderson claimed four of the seven wickets before lunch, the other three went to Onions, and finished with 5-25 from 17 overs. Eighteen of Anderson’s hauls of five wickets have come for Lancashire.
Onions claimed the first two wickets, Daryl Mitchell caught at first slip by Keaton Jennings and Tom Fell lbw.
Anderson uprooted George Rhodes’ off-stump with the next delivery (6-3), then trapped Riki Wessels and Callum Ferguson lbw (21-5) before Onions bowled Ross Whiteley. When Anderson had Ed Barnard caught at second slip by Liam Livingstone, Worcester were 38-7 in the 19th.
Then came the recovery, led by Parnell, who helped the score to 66-7 at lunch. Further improvement followed, with Ben Cox (32) and captain Joe Leach contributing (36).
Wicketkeeper Cox shared in a stand of 52 only to under-edge Richard Gleeson behind at 90-8. Lech counter-attacked with six fours, including three in one over from Gleeson, in a 61-run partnership.
The Worcester skipper, playing only his second game after nearly a year out with a back injury, was caught behind off Anderson.
Parnell reached his 50 off 108 balls with five fours and hit seven in all, only to be bowled by Tom Bailey to wrap up the innings on the verge of tea.
The day started with Lancashire announcing that Australian Joe Burns had cut short his stint for personal reasons and returned to Brisbane after one game. Jake Lehmann, who featured in the Royal London One-Day Cup, has stepped in.
Lehmann was one of the five Red Rose wickets to fall. Leach had Jennings caught by Fell before Parnell had Lehmann too caught behind by Wessels. Charlie Morris trapped Haseeb Hameed lbw for 29 before Parnell had Rob Jones (25) caught by Mitchell and nightwatchman Anderson lbw.