Tenants on a London housing estate where protests erupted after it was bought by a consortium including a Tory MP’s property company say they fear eviction before Christmas after the new owners rescinded a deal to delay huge rent rises.

The New Era estate in Hoxton, a 1930s square of flats in a fast-gentrifying part of east London, which had until now provided affordable rents to local people, was bought this year by Westbrook Partners, a US-based private property investment group that has been targeted by officials in New York over lack of repairs and overcharging.

Westbrook passed management of the homes to the Benyon Estate, co-owned by the Conservative MP Richard Benyon and run by his brother, which bought a small stake. However, on Friday, following a wave of negative reports about their plans for the estate, the Benyons announced they were pulling out as residents had “made it clear that they do not welcome our involvement”.

As residents celebrated an apparent victory in a campaign that has attracted support from Russell Brand among others, on Saturday four Hackney councillors hand-delivered letters warning of Westbrook’s new plans.

The councillors, including Philip Glanville, Hackney’s cabinet member for housing, said they had previously urged Benyon and Westbrook not to increase rents on the estate to market values, which in some cases would lead to a rise from about £600 a month to nearer £2,400, calling such a move unacceptable.

The letter said they had secured an agreement not to increase rents again until 2016. However, it added: “Since this week’s departure of the Benyon Estate we understand the council have now been informed that Westbrook no longer plan to honour that plan, and have been told that their plan is to refurbish the current estate in its entirety and then rent all the properties without secure tenancies at market rent levels, with no affordable housing.”

Lyndsey Garratt, 35, an NHS care coordinator who has been one of the leaders of the New Era campaign, said the councillors had told her that Westbrook’s intention appeared to be to remove existing families as fast as it could before renovating the estate and renting the flats at market rates to new tenants.

Of the 93 New Era flats, she said, all but seven or eight were rented on contracts with two-week break clauses, meaning families could be evicted before Christmas. The earlier promises about no new rent rises had never been formalised, she added.

Garratt said: “According to Hackney council the evictions could be asap. They’re in the process of organising a meeting between us and Westbrook, even though I can’t really see them coming down here.”

Residents would resist, she said: “The bottom line is that the support for us has been incredible. The momentum is growing on a daily basis. The idea that they’re going to evict all these families in the next few months – it’s just nuts. It’s not going to happen. I think it shows signs of weakness by Westbrook that they’re acting in such a desperate way.”

Garratt said she had seen no support from the local Labour MP, Meg Hillier, or the mayor of London, Boris Johnson. “Boris seems happy for people to come into London, start buying up property and kick people out,” she said. “So he’s going to be getting targeted by us, unless he steps up and does something about it.”

The estate – three separate four-storey buildings – was constructed in the mid-1930s as affordable family homes and remained in the same ownership until this year. Details of the sale to the Westbrook-led consortium are unclear.

While much of the initial focus was on Benyon Estate, the MP’s company has argued it was unfairly maligned and became involved mainly to help temper Westbrook’s actions. In a statement to the Guardian, the firm – which has owned properties in the area for more than 150 years after the brothers’ great-great-great uncle first developed the area known as De Beauvoir Town – said: “We accepted the invitation to become involved, and to take this comparatively small stake, because we thought we could play a positive role that would benefit our partners, our tenants and the local community. But it’s impossible to play that kind of role when the tenants don’t want you there.”

Attention has now shifted to Westbrook, a multinational company whose London portfolio of properties also includes Dolphin Square, a block of 1930s apartments in central London long popular with MPs.

In April, Westbrook was labelled a “predatory landlord” by tenants in Three Borough Pool, a group of 44 buildings in the Bronx, Brooklyn, and Manhattan.

After protests outside New York city hall, the US attorney general, Eric Schneiderman, forced Westbrook and the three other owners of Three Borough Pool to make repairs to the 1,592 properties, resolve thousands of building violations and provide tenants with more than $1m in rebates for illegal fees and overcharges.

Staff who answered the phone at Westbrook’s London office last week said they did not know who was able to speak to the press and were unwilling to ask colleagues. The London operation is headed by a British national, Mark Donnor, a 40-year-old chartered surveyor with an interest in racing classic cars. He could not be reached for comment.

In a statement on Sunday the owners of the estate said they had appointed property services firm Knight Frank to take over the management of the estate in place of Benyon. The company would work with Knight Frank “to assess its plans for the future of the estate”, it said, adding that as yet no rents had risen beyond 10%.

The statement was issued on behalf of Hoxton Regeneration Ltd, which is officially separate from Westbrook but has senior Westbrook staff as its only directors.