New Zealanders returning home must currently spend two weeks in a managed isolation facility, but there's a severe shortage of rooms and thousands of people have been unable to secure a place.
MIQ spots must be booked through a virtual lobby system - more than 19,000 people flooded the system on Thursday afternoon when just 2100 slots were released.
The Chief Ombudsman has launched an inquiry into the MIQ booking system following hundreds of complaints.
Act leader David Seymour said the party sympathised with and endorsed the banner. "MIQ does suck and we should let them come home," he said.
He said All Blacks games were usually a chance to promote New Zealand on the world stage - but "today the world has seen that we're treating off-shore New Zealanders with contempt".
"Jacinda Ardern keeps talking about the team of five million. We're actually a team of six million, there are a million Kiwis offshore who still call New Zealand home who have no pathway to coming back.
"People want to come for many reasons. Family reunions, deaths of loved ones, the arrival of new babies, to fill jobs, and just being with family and friends. New Zealand is their home, keeping them locked out and fighting over a tiny number of MIQ spaces is cruel."
Act would let fully vaccinated people self-isolate if they have tested negative, he said - pointing out there were already more than 80 people in Auckland who were isolating at home with Covid-19.
