The eighth Silent Walk to commemorate those who died in the Grenfell Tower fire was set to take place on Wednesday.
The family of one victim, Khadija Khalloufi, has accused the Home Office of effectively blocking them from taking part in a public inquiry into the fire.
The family has been granted core participant status, but are still waiting for visas after applying in December.
They say they handed over their passports at the British visa centre in Rabat, Morocco.
Shadow home secretary Diane Abbott said, “The public were assured that no stone would be left unturned.
“But how much confidence can they have when core participants can’t even enter the country?
“The government must ensure that immigration status is not a barrier to the truth about Grenfell.”
Meanwhile FirstPort, which owns the Citiscape block in Croydon, wants residents to pay to remove cladding, reclad the tower and cover fire wardens’ wages.