US investors who planned to evict dozens of families and more than double rents at the New Era estate in east London are on the verge of selling it to an affordable-housing provider after a vocal campaign against their ownership.

Westbrook Partners, an $11bn asset management firm with offices in Manhattan and Mayfair, is close to agreeing the transfer following negotiations with London’s deputy mayor, Richard Blakeway, and the elected mayor of Hackney, Jules Pipe, the Guardian has learned.

The new deal for the estate has been forged between the current owners and an unidentified social landlord already operating in London. The Guardian understands City Hall privately expects the sale to go through before Christmas. It would represent a dramatic climbdown by Westbrook, which was set to make a significant profit by increasing rental yields before selling on the Hoxton estate, which is located just north of the City on the fringes of one of the most fashionable areas of the capital.

The New Era estate in Hoxton, east London. Photograph: Graham Turner Photograph: Graham Turner/Guardian

Families had been distraught after Westbrook’s takeover and feared being evicted before Christmas. Some had planned to barricade themselves in. They said Westbrook’s plan to increase rents from around £800 a month for a two-bedroom flat to more than £2,000 amounted to social cleansing.

The previous owners had kept rents at below market values, allowing several generations of families to stay in their homes and maintaining a close-knit community. Some of the families said the increases would force them out of London, causing them to lose jobs and school places.

The terms of the draft deal are said to mean the homes will remain as private rented accommodation rather than becoming social housing, but the new owner is believed to have offered some guarantees about rent levels for at least a year. It will then look at how to set future rents, which is likely to mean increases. Residents greeted the news on Thursday night with a mix of delight and caution. “This is brilliant news and a victory,” said Lindsay Garrett, chair of the New Era residents’ association. “If they are going to offer us affordable long-term rents, we welcome it. But they have to put the deal on the table. We will continue to make sure the residents get the best deal we can. Anyone who comes into this estate and takes it on will do so with trepidation.”

The sale is likely to send shockwaves through the booming international investment market in central London homes. Investors from America, Malaysia, China and Singapore have bought housing sites in the capital amid forecasts by the agency Savills that prices will rise 25% over the next five years.

Westbrook faced a storm of opposition. Senior Labour figures, including the shadow London minister, Sadiq Khan, joined the Conservative mayor, Boris Johnson, in demanding that they rethink their plans.

Three women who live on the 93-home estate mounted a vociferous and media-savvy campaign. They enlisted the support of Russell Brand, who lives nearby, and organised hundreds of residents and other supporters to march on Westbrook’s UK offices in Berkeley Square last month to deliver a 300,000 signature petition to David Cameron, calling on him to save their homes.

Comedian Russell Brand joins residents and supporters of the estate as they deliver their petition to 10 Downing Street. Photograph: Dan Kitwood/Getty Images

Sources involved in negotiations over the future of the estate said that, while the likely deal gave hope that residents would be able to look forward to more secure tenancies and lower rents than if Westbrook had continued with its plans, the terms of the new tenancies are not yet known.

Johnson gave a clear sign on Wednesday that a deal was imminent. During an event at City Hall he said: “We are very sure that there is a favourable and a fair outcome for the tenants who, I agree, had the shock of seeing their rents potentially go up, and what I want to achieve is the sale of that estate to a social landlord.”

Asked by Labour’s Tom Copley if the mayor was asking Westbrook to sell the estate, he said: “I think that would be not a bad outcome and obviously we are not there yet but think that would be a reasonable way forward, yes.”

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At a public council meeting on Monday, Pipe reportedly told residents that he was hopeful of a sale.

Westbrook had showed earlier signs of responding to the pressure. On the last day of November the owners told the tenants there would be no changes to the tenancy agreements and no increase in rents during the first half of 2015.

The firm bought the estate in March with the Benyon Estate, the family property company of the Conservative MP for Newbury in Berkshire, Richard Benyon. The Benyon Estate had a stake of less than 10% and acted as managing agent, but it pulled out in November after residents protested outside the company’s offices. The firm said the residents “made it clear that they wanted us to pull out, and this is what we have reluctantly decided to do”.

The Guardian approached Westbrook Partners for comment but they did not respond before publication.