Millwall created the better chances in the first half with Andy Keogh, Liam Trotter and James Henry all going close and Chris Wood having a goal disallowed for off side.
Ipswich went on to claim a 3-0 victory with two goals from DJ Campbell and one from Daryl Murphy, leaving Jackett frustrated with the officials and his side's failure to get ahead.
"We should have been a goal ahead," he said. "Wood's (disallowed) goal from Lowry's pass was clearly onside, having seen it again, but we've gone in 1-0 down.
"Their keeper has made three very good saves and we've had an onside goal disallowed.
"We could have been one or two up in that period, but instead we found ourselves 1-0 down.
"The start of the second half was poor for us. Two poor goals took the game away from us.
"We've been defending very well, but Murphy and Campbell were a handful for us and made key contributions for Ipswich.
"We kept going and battling but couldn't quite make a breakthrough, to get back in the game.
"Ipswich had an intensity but we needed that goal in the first half to give us something to build on."