Residents of east London estate stage demo at Westbrook Partners’ HQ in Mayfair to protest against plans to evict them Follow Monday’s protest live

Residents of housing estate in east London have travelled to the offices of the US investment company that has bought their homes to protest against its eviction plans.

Parents, children and grandparents from the New Era estate in Hackney travelled across the capital on buses to the Westbrook Partners HQ in Mayfair amid growing political support for their cause and a new agreement by the company not to change tenancy agreements or increase rents before July 2015.

The comedian and political activist Russell Brand, the Labour MP Diane Abbott and the leaders of the tenants’ group are to lead the protest and then march to Downing Street to present a petition to the prime minister. Almost 300,000 people have signed the petition, which calls for the owners to keep rents at an affordable level so existing tenants can afford to stay.

The shadow minister for London, Sadiq Khan, called on Westbrook to scrap its plans to evict 93 families from the estate and instead sell the homes to a social landlord that can keep the community together.

Speaking to the Guardian before the protest at Berkeley Square on Monday lunchtime, he said: “The shameful New Era saga embodies everything that is wrong with London’s broken housing market.”

Westbrook bought the housing estate in Hoxton in March and transferred its ownership to an offshore company in the Channel Islands tax haven of Jersey. The firm is understood to be planning to evict the tenants, refurbish the estate and re-let the flats at full-market value – which in some cases could be three times higher than current rents. Westbrook has only made assurances that rents will not go up before the turn of the year.

“Ordinary Londoners are suffering, with their homes ripped from underneath them and their lives and families pulled apart, just so international investors can make a quick buck, with no regard to the community they are destroying,” said Khan.

“If Westbrook won’t provide affordable housing to families on the estate they should sell to a social landlord who can keep the community together.”

Hackney council believes Westbrook does not want a long-term commitment to the estate, which has led to speculation that the company will sell the estate again within a few years once its value has increased after raising the rents.

On Sunday night, letters were hand-delivered to all tenants in which the new owner said: “There will be no changes to the tenancy agreements and no increase in rents during the first half of 2015.

“To help us work with you more closely we will also be appointing a dedicated tenant liaison officer … We understand the accusations about us and our plans have caused concern and distress amongst tenants, so we hope that these commitments provide some further reassurance.”

Lindsay Garrett, chairwoman of the New Era residents association, said the letter only deferred the eviction plans.

“Westbrook are hoping this will die down and we are going to go away but we won’t because we haven’t got anywhere else to go,” she said.

Hundreds of people are expected to attend the protest in Berkeley Square, which is being organised by residents and their families. Brand, who has thrown his weight behind the residents’ campaign, is expected to speak alongside resident leaders including Garrett.

Support for their campaign has been widening in recent days and backers include the children’s author Michael Rosen and the comedian Mark Thomas.

The protest comes as negotiations between senior London politicians and Westbrook’s managing principal, Mark Donnor, continue. Over the last 10 days, the company has held meetings with Richard Blakeway, London’s deputy mayor for housing, Meg Hillier, the tenants’ Labour MP, Jules Pipe, the elected mayor of Hackney, and Philip Glanville, the cabinet member for housing at the council.

Pressure is now growing on the London mayor, Boris Johnson, to act.

Hackney is proposing that Westbrook sells the homes to a social housing organisation, but in the absence of clear powers to force the private company to act, the negotiations are understood to be delicate. Last week, Bill de Blasio, the mayor of New York – where Westbrook is based – spoke out against the firm.

“Congratulations. London is experiencing what New York City used to experience,” he told Brand in an interview broadcast on the comedian’s Trews show on YouTube.

“Our city government found a huge number of violations of our law by Westbrook for unfair treatment of tenants and attempts to interfere with tenants who organised for their own rights.

“I can’t tell you that what you are experiencing is news to us … Sometimes it is fair to say there is a limit to the amount of profit you should make, because you shouldn’t want to dislocate people from their lives.”

In April, Eric Schneiderman, the attorney general of New York state, ordered Westbrook and other private equity owners of series of housing complexes in the city to payback $1m (£650,000) in fees and overcharges to almost 1,700 tenants and make urgent repairs.

It followed residents’ complaints about “dangerous” conditions at the blocks and allegations that the owners’ management company, Colonial Management, blocked tenants and housing activists from organising and used intimidation tactics to break up peaceful meetings.

There is no suggestion of similar problems at the New Era estate.

In a statement issued last week Westbrook said: “We take our responsibility as a landlord very seriously and are committed to working closely with our tenants throughout this period … We are committed to engaging in constructive dialogue with tenants, their representatives and interested local parties.”

It said it will not change any tenancy agreements or rent levels until 2015 and that this will only be done after meetings with residents, which it wants to conduct on an individual basis.

Khan, who is thought likely to bid for the Labour candidacy for London mayor, said the situation showed “we need more affordability and stability in rented accommodation and a national register of landlords so councils can run licensing schemes which would stop this sort of abuse”.