The local resident and 'Smile' star made the shock claim during a Channel 4 interview with Jon Snow.
She also claimed that the government were trying to "micromanage" people's grief.
Police have revealed that 17 people have died so far as a result of the fire but have warned that number is expected to rise in the coming days.
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However, Allen said that she has heard from "off the record numbers" given to her from policemen and firemen, that the figure is closer to 150.
During her Channel 4 interview, she said: "If we are talking about bringing reality into these people's lives, I think what people would really like is a more honest count of how many people have actually died in this event, how many people have been killed.
"I feel like the government are trying to micromanage people's grieving here.
"I have never in my entire life seen an event like this were the death count has been downplayed by the mainstream media.
"Seventeen? I'm sorry but I am hearing from people the figure is much closer to 150 - and that many of those people are children.
"They are off-the-record numbers I have been given from policemen and from firemen."
Presenter Jon Snow attempted to interject and said the difficulty is having to identify bodies and said there was "very little left in this building".
Allen responded: "Why is that not coming out now?
"I don't understand."
The search for the bodies of those killed in the Grenfell Tower inferno is still continuing with more than 70 people believed to be unaccounted for since the blaze.
Six bodies have been recovered from the gutted 24-storey tower, while 11 have been located inside, but cannot yet be removed.
Metropolitan Police commander Stuart Cundy responded to speculation that the number of dead could exceed 100, saying: "For those of us that have been down there, it's pretty emotional, so I hope it is not triple figures, but I can't be drawn on the numbers."