A homeowner in a housing complex in London with Grenfell-type cladding has been told the value of her £475,000 home has collapsed and is now just £50,000.

Galliard Homes, the developer of the 11-block complex in New Capital Quay in south-east London, is facing a £30m-£40m bill to replace the cladding and is locked in a legal dispute over who should pay.

The dispute, which could take years to resolve, has left Mary Tlick (not her real name) and potentially thousands of others up and down the country, with an unsellable flat.

“It is like someone has taken away our life choices, our freedom,” she said. “And nobody is doing anything about it,” she added, in tears.

Tlick has a two-year-old son and was due to give birth to her second child on Saturday. She had put their flat on the market in the hope of moving out of London to a bigger home.

She got a Rics-approved surveyor to value her flat recently and was shocked when he came back with a £50,000 price tag. But now she realises the whole complex is blighted.

“All ongoing sales in the development have fallen through. Banks are not lending to potential buyers and provide valuations of zero for flats in our development,” she said.

Tlick is one of about 2,000 residents in NCQ in Greenwich, believed to be the largest private development found to have flammable cladding after the west London disaster that cost 71 lives.

“I don’t sleep at night. I wake up most nights for a few hours and I write emails to people I think that can help,” said Tlick.

“I can’t move very fast. What would happen if my husband was away one night? We are on the seventh floor. What if if I was there with my son and new baby and all the people were at the stairs and I couldn’t get out?” she asked.

While cladding remains on such buildings, the fire brigade requires 24/7 fire patrol in case evacuation is needed, but in three cases so far in private blocks, including one in Croydon and another in Salford, this has meant leaseholders will face bills potentially of tens of thousands of pounds.

“It is quite shocking that the residents are living in potential death traps while everybody else tries to deny liability for the cost of making them safe. There is the potential for the residents to bring group legal proceedings to recover the cost of fixing the buildings and for the considerable distress they must be suffering,” said Chris Haan, a lawyer at the London law firm Leigh Day.

He has been approached by a number of home owners in NCQ and said they may have a case against the developers for breach of contract when they sold homes “fit for habitation when completed”.

Tlick funded the flat in 2014 through some savings, a mortgage with a high-street bank and a £95,000 government loan under the Help to Buy scheme designed to help people without enough savings to get on the property ladder.

She said she could repay that loan without selling, under the government’s rules. But she believes she has to repay only 20% of the market value, which at £50,000 means she would owe £10,000 and the government would lose £85,000 of its loan to her.

Tlick believes that many other homes in the NCQ development were purchased on the Help to Buy scheme, which was heavily promoted by Galliard at the development’s launch.

She has had no answer from Target HCA, which is administering the scheme, other than to say it is a “novel” request.

“They are being evasive, because they know if they have to do this for me they have to do it for everyone who asks,” she said.

Regardless of how much of the government loan she has to repay, Tlick is still subject to huge negative equity because the value of the flat has plummeted.

She said she is at her wits’ end and suffering from stress over her situation. She said she can’t move out and rent to others because she would feel terrible “if they were caught in a fire”. It is also not permissible under her Help to Buy contract.

She contacted the housing minister, Dominic Raab, but he did not reply. “I don’t think he cares about ordinary people,” she said.

It is likely that thousands of private homeowners are in Tlick’s situation, with government data showing 301 blocks over 18 metres tall have Grenfell-type cladding, of which 130 are in the private sector and 13 are hospitals or schools. Of the public buildings, only seven have had their cladding replaced so far.

A spokesman for the Ministry of Housing, Communities and Local Government said: “We have made clear that we want to see private sector landlords follow the lead of the social sector and not pass on the costs of essential cladding replacement to leaseholders.

“We are keeping the situation under review and ministers are meeting industry representatives shortly to discuss this.”

Campaigners said the cladding was causing financial ruin for homeowners.

“The blight caused by Grenfell is national and the government doesn’t seem to be too bothered about that. So far, what we have heard from Greenwich and Croydon is just the tip of the iceberg,” said Martin Boyd, a trustee at the charity Leasehold Knowledge Partnership, a service that advises leaseholders on their rights over cladding and other issues.

Galliard Homes declined to comment.

• This article was amended on 10 March 2020 to remove some personal information.