Frances McDormand said it is “really exciting” that the film she won an Oscar for inspired people to campaign about the Grenfell Tower fire.
Last month the Justice 4 Grenfell group hired vans with adverts which read: “71 dead. And still no arrests? How come?”
The parade mimicked scenes in Three Billboards Outside Ebbing, Missouri, where McDormand’s character demands answers about her daughter’s murder.
A police investigation into the fire is ongoing and no arrests have been made.
After winning the gong for best actress, McDormand said she enjoyed seeing billboards moving “off the screen and onto the street”.
“Activists are taking that kind of statement and putting it out there – billboards still work, so I think that it’s really exciting,” she added.
“It started actually with the Grenfell Tower fire investigation then it leap-frogged to (the) Miami gun control situation.
“It was outside the UN… that’s the kind of power that an image can have and that’s what we’re making, we’re making powerful images.”
Moyra Samuels, one of the organisers of the Grenfell stunt, compared McDormand’s “very positive” words with the reference to the fire Stormzy made at the Brit Awards.
“It’s not just politicians who are taking note of what happened, realising that it’s not being dealt with effectively by both the council and the government,” she said.
“We are being effective at raising the issues on a worldwide stage.”
Kim Taylor Smith, deputy leader of Kensington and Chelsea council, said there is an “army” of 300 staff members “working around the clock, doing everything they can” to rehouse survivors of the blaze, which killed 71 people last June.
The council has spent £235m to secure 307 homes, she added.
The government is yet to respond to a request for comment.
Ms Samuels said the Grenfell billboards combated “campaign fatigue” by reminding the public of the “broken promises and unfulfilled needs” ongoing after the fire.
A petition calling for Prime Minister Theresa May to take action to build public trust in the inquiry into the fire has reached 100,000 signatures – the number needed for it to be considered for debate in Parliament.