London mayor Sadiq Khan has branded the EU Settlement Scheme a failure as figures show almost two thirds of people in Camden have failed to register.
Some 58.7 per cent of people in the borough have not applied for settled status as of September, along with 44pc of EU citizens in Haringey and 35pc of those in Brent.
The figures were published by City Hall using the latest Home Office Settlement figures and an Office for National Statistics (ONS) population survey from 2018.
They also report only two per cent of over 65s and 18pc of under 18s have registered.
Speaking to this paper, Mr Khan said: "The evidence so far is yes [it is failing]… What we do know is that the government scheme has only had 60pc of people, roughly, registering, so 40pc haven't registered; that's 438,000.
"What's also troubling is the government's record of formalising immigrants. Look at Windrush and the scandal there."
Of the 66,000 EU nationals in Brent, 23,630 haven not applied, along with 23,630 of 54,000 in Haringey and 21,740 of 37,000 in Camden.
Mr Khan joined a roundtable of women from Brent's Romanian community in Queens Park yesterday, along with Hampstead and Kilburn incumbent Tulip Siddiq.
He said people were not registering because they were either technologically illiterate; feared their data being used against them; or confused by the government's message on Brexit.
Alini Balatchi, co-founder of the charity Romanian Women in the UK, was at the event and said her charity stopped hosting Brexit seminars for EU citizens because of the government's mixed messages about leaving.
She believes the number of unregistered EU citizens could be higher than current estimates. She said: "There are 100,000 Romanians registered to work in the UK. Government figures estimate there are between 430,000 to 600,000 living here. I think that number is closer to 800,000 when you factor in children."
Ms Balatchi said there are currently 20,000 Romanians living in Brent and 22,000 in Harrow. ONS records show more than 15,000 babies were born to a Romanian parent last year, the highest birth rate of any Romanian expat community in the world, according to Ms Balatchi.
She said abuse against her community has steadily risen over the years. She said: "At least two-thirds of us have been victims of abuse. Most of it occurs over Twitter. What people don't understand is that most of us are actually British. We hold Romanian and British passports.
"Even more alarming is that landlords and employers are now asking for proof of settlement status from EU citizens. There is no law saying we need it or that we need to prove it."
A Home Office spokesperson said City Hall's figures were misleading and counted people staying temporarily.
"Figures in this report include non-EEA family members, Irish nationals, and eligible EEA citizens not resident in the UK, none of whom are usually included in estimates of the resident EU population," they added.
The Home Office has spent £9million across 57 organisations to help people register.
Mr Khan and Ms Siddiq's visit comes as political parties gear up for the final fortnight of electioneering.
Ms Siddiq, who is defending a majority of 15,560, told this paper a vote for her would mean a vote against austerity and the current Brexit deal. She also wants to introduce automatic vetting for new candidates in the Labour party and bolster the investigation process for antisemitism complaints.
She said: "I've spoken up against antisemitism a number of times, with Jeremy Corbyn and with others and I've made sure they've listened. It should have been quicker action but I'm confident we can get party back to where it was."
Today coincides with this year's "homeless count" across the capital. Between 2008 and 2016, the number of rough sleepers doubled from 8,000 to 16,000, according to the mayor.
He said: "This is a disgrace in one richest city in the world. Since I become Mayor, I have doubled funding addressed to issue rough sleeping and doubled frontline workers. We've also changed concerning emergency night centres. Before, they only opened when it got to zero degrees three nights in row, now we open them if it happens one night."
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